Clinical Flashcards

1
Q

Causes of primary ovarian insufficiency (POI)

A
  • Idiopathic
  • Turner syndrome
  • Premutations for Fragile X
  • Autoimmune (may be part of polyglandular syndrome)
  • Toxicity to ovaries - chemoTx, RadioTx
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2
Q

Physiological stimulators of GH secretion

A

Hypoglycaemia
Fasting
Starvation
Exercise
Stress and trauma
Sepsis
Insulin

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3
Q

GH secretion is inhibited by..

A

Hyperglycaemia
Increase in free fatty acids in blood

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4
Q

Hereditary causes of methaemoglobinaemia?

A

HbM

Cytochrome b5 reductase deficiency

G6PD deficiency (however minor role compared to cytochrome b5 reductase)

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5
Q

Acquired causes of methaemoglobinaemia?

A

Medications e.g. Benzocaine; dapsone; primaquine
Chemical agents e.g. chlorobenzene; silver nitrate
Nitrate containing foods

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6
Q

What clinical signs/findings lead to a diagnosis of methaemoglobinaemia?

A

Cyanosis unresponsive to oxygen
Chocolate coloured blood
Saturation gap of >5% (difference between pulse oximeter and multiwavelength oximeter)

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7
Q

Methods to confirm presence of increased Met-Hb?

A

Multiwavelength oximeter on blood gas instrument

Evelyn-Malloy test (add cyanide to bind with Met-Hb and amount of absorption elimination is proportional to Met-Hb)

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8
Q

What factors other than GnRH regulate FSH secretion?

A
  • Inhibin - inhibits FSH secretion
  • Activin - activates FSH secretion
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9
Q

Causes of decreased IGF-1

A
  • GH deficiency
  • Malnutrition
  • Liver failure
  • Renal failure
  • Hypothyroidism
  • Poorly controlled DM
  • Severe infection
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10
Q

Differentials for neonatal jaundice - predominantly conjugated

A
  • Biliary atresia
  • Idiopathic neonatal hepatitis
  • Infection: TORCH infections
  • TPN
  • inherited disorders of bilirubin metabolism (Dubin Johnson; Rotor syndrome)
  • other inherited disorders (A1AT def; CF; galactosaemia; tyrosinaemia)
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11
Q

Causes of hypopituitarism

A

Mass lesions
Pituitary surgery
Pituitary radiation
Drug induced e.g. IFNalpha; immune checkpt inhibitor
Infiltrative lesions e.g. hypophysitis, haemchromatosis
Infarction (Sheehan syndrome)
Apoplexy
Genetic mutations
Empty sella

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12
Q

Typical order of affected hormones with hypopituitarism

A
  1. Hypogonadism
  2. GH deficiency
  3. ACTH
  4. Hypothyroidism
  5. Prolactin - rarely deficient
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13
Q

With what causes of hypopituitarism is ACTH secretion more likely to be affected? (name 2)

A

Lymphocytic hypophysitis
Immune checkpoint inhibitors

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14
Q

What does MELAS stand for?

A

Mitochondrial
Encephalomyopathy with
Lactic
Acidosis and
Stroke-like episodes

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15
Q

What does LHON stand for?

A

Leber
Hereditary
Optic
Neuropathy

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16
Q

What happens to SHBG in TSHoma vs thyroid hormone resistance?

A

Elevated in TSHoma
Normal in thyroid hormone resistance

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17
Q

What happens to alpha subunit in TSHoma?

A

Elevated alpha subunit: TSH ratio

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18
Q

Tumours associated with MEN1?

A
  1. Parathyroid
  2. Pituitary adenomas (e.g. prolactin; non-functioning; acromegaly)
  3. Pancreas (e.g. non functioning; gastrinoma; insulinoma)
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19
Q

What proportion of Familial isolated hyperparathyroidism have MEN1 mutation?

A

20%

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20
Q

What gene is affected in MEN2?

A

RET (oncogene)

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21
Q

What gene is affected in Wilsons disease?

A

ATP7B gene - affects the function of the ATPase2 membrane protein

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22
Q

What does POMC stand for?

A

Pro-opio-melanocortin

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23
Q

What hormones are produced by the corpus luteum?

A

Steroids: E2, progesterone
Non steroids: Relaxin, VEGF

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24
Q

What are the criteria for successful cannulation with AVS?

A

Adrenal vein cortisol/Peripheral vein cortisol
>/=2 at baseline
>/=3 post ACTH stimulation

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25
In an AVS test, what Aldosterone:Cortisol Ratio between the 2 adrenals indicates lateralisation?
>4 indicates lateralisation (ACTH stimulation) >2 may indicate lateralisation in unstimulated AVS
26
In an AVS test, how do you determine if there is contralateral suppression?
The unaffected adrenal gland should have an Aldosterone:cortisol ratio (ACR) less than the peripheral ACR
27
Differentials for Aldosterone Resistance
Medications that inhibit the epithelial sodium channel - Potassium sparing diuretics (spironolactone, epleronone, amiloride, triamterine) - Antibiotics - trimethoprim; pentamide Pseudohypoaldosteronism type 1 Pyelonephritis Obstructive uropathy
28
What are the features of pseudohypoaldosteronism type 2 (Gordon syndrome)
Autosomal dominant condition Hypertension Hyperkalaemia Metabolic acidosis (Normal Cr) Low renin and aldosterone Hypercalciuria, hypocalcaemia Treated with thiazide diuretics
29
Causes of increased DHEAS
- CAH - Cushings - Adrenal tumour - PCOS
30
Causes of transiently elevated prolactin
- Recent seizure - Drug related - Breast feeding - Post coital elevation - Rarely Pituitary apoplexy
31
Differentials for secondary HTN in young woman
- Primary hyperaldosteronism - Renal artery stenosis - Parenchymal renal disease - consider collagen disorders such as SLE - catecholamine producing tumours - Cushings
32
A bilateral total adrenalectomy in association with ACTH-dependant Cushing’s may result in which syndrome?
Nelson syndrome
33
Causes of central diabetes insipidus?
Pituitary tumour Neurosurgery Head trauma
34
Causes of nephrogenic DI?
Lithium Renal Dx Hypokalaemia Pregnancy
35
What is the cofactor for AST and ALT?
Pyridoxal-5-phosphate
36
What are 2 confounding factors in interpreting the level of plasma P5P
Albumin (plasma P5P is bound to albumin) ALP (degrades P5P)
37
Risk factors for P5P deficiency?
Elderly Alcoholism Coeliac disease
38
What changes in LFTs would be expected with increased weight/obesity?
ALT increase (note more significant increase with weight/metabolic syndrome than AST or GGT)
39
What are the half lives of ALT and AST?
ALT 36hrs AST 18hrs
40
What is the half life of CK?
12hrs
41
What is the half life of albumin?
15-19 days
42
Causes of increased loss of albumin?
Nephrotic syndrome Severe blood loss Burns
43
Causes of low albumin relating to increased metabolism?
Sepsis Burns Malignancy Hyperthyroidism
44
What happens to albumin in inflammation?
Reduced concentration due to decreased synthesis (inhibition by IL-6 , TNF)
45
What does SAAG stand for?
Serum ascites albumin gradient
46
What does SAAG of 11 or above indicate?
Ascites secondary to portal hypertension (e.g. CCF, cirrhosis, alcoholic hepatitis)
47
What does SAAG < 11 indicate?
Ascites not associated with portal hypertension (e.g. nephrotic syndrome, pancreatitis, peritoneal carcinoma, TB)
48
What is the Payne formula for corrected calcium?
Corrected calcium = Total calcium + 0.02 x (40 - Albumin)
49
What is the toxic metabolite that increases in paracetamol overdose and causes hepatic necrosis?
NAPQI (N-acetyl-p-benzoquinoneimine)
50
Causes of increased intestinal ALP?
Blood groups O and B - especially after a fatty meal Cirrhosis T2DM Inflammatory bowel disease
51
Causes of low ALP
Pre-analytical - EDTA or citrate contamination Hypophosphatasia Zn and Mg deficiency Untreated hypothyroidism Bisphosphonates Wilson disease
52
What can be used to separate bone and liver ALP on gel electrophoresis?
Neuraminidase (other option is Lectin)
53
Biochemical findings in hypophosphatasia?
↓ALP ↑B6 in serum ↑ PEA in urine
54
What reduces NAPQI to nontoxic mercaptate and cysteine compounds for renal excretion?
Glutathione
55
Name 2 prognostic scoring systems for severe liver disease?
Child-Turcotte-Pugh MELD (Model for End-stage Liver Disease)
56
Causes of decreased albumin
- Inflammation - Decreased production (severe liver disease) - Increased loss (e.g. nephrotic syndrome) - Haemodilution (e.g. pregnancy)
57
Formula for "R ratio" of LFTs
(ALT/ALT URL)/(ALP/ALP URL)
58
What does a LFT "R ratio" of >5 indicate?
Hepatocellular damage
59
What does a LFT "R ratio" of <2 indicate
Cholestasis
60
Name the 4 types of ALP isoenzymes
- Tissue non specific (Liver/Bone/Kidney) - Intestinal - Germ cell - Placental
61
Medications that can cause a false positive ARR due to reduced renin
Beta blockers Methyldopa Clonidine NSAIDs OCP
62
What medications can give false negatives of ARR?
ACE inhibitors Angiotensin II receptor antagonists Calcium channel blockers (Dihydropyridines) Diuretics Spironolactone
63
What is the impact of posture on aldosterone and renin?
Increase with standing (more pronounced increased for renin)
64
How are aldosterone and renin influenced by time of day of blood collection?
Circadian variation is significant for aldosterone - similar pattern to cortisol Renin is also higher in morning and falls throughout the day
65
What is the potential impact of the luteal phase on ARR?
False positives are more likely in luteal phase (Increase aldosterone and decrease renin)
66
Classic biochemical findings in salicyclate toxicity?
Respiratory alkalosis (hyperventilation) followed by metabolic acidosis (due to accumulation of organic acids) Hypoglycaemia Hypokalaemia, Hypercalcaemia
67
Biochemical Profile of HELLP syndrome (ACOG requires all 3)
LDH> 600 AST and ALT more than 2 x URL Platelets < 100,000 cell/micro/L
68
Differentials for HELLP syndrome
Pre-eclampsia Acute Fatty Liver of Pregnancy
69
Biochemical profile of Acute Fatty Liver in Pregnancy (Swansea criteria)
Elevated total bilirubin Elevated AST or ALT Elevated Urate AKI Coagulopathy Hyperammonaemia Hypoglycaemia
70
Presenting symptoms of Obstetric Cholestatis
Occurs 2nd half of pregnancy Pruritus RUQ pain Nausea Steatorrhoea Jaundice
71
Biochemical Profile of Pre-eclampsia
AST and ALT >2 URL Proteinuria (>0.3g in 24 hrs) Hyperuricacidaemia Raised creatinine Thrombocytopaenia Elevated s-Flt to PlGF ratio
72
What is the role of sFLt-1 to PlGF in assessment of pre-eclampsia?
High ratio -> indicates increased risk Low ratio - can help rule out pre-eclampsia occuring within the next 2 weeks
73
Which inherited disorder has been associated with acute fatty liver in pregnancy?
Fetal long-chain 3-hydroxyacyl CoA dehydrogenase (LCHAD) deficiency
74
Clinical Features of obstetric cholestasis
Occurs 2nd half of pregnancy Pruritus RUQ pain Nausea Steatorrhoea Jaundice
75
Biochemical profile of Obstetric Cholestasis
Elevated bile acids (cholic acid; Chenodeoxycholic acid) Elevated bilirubin AST, ALT mild rise ALP/GGT increased
76
Which form of iron is taken up by DMT1 in the duodenum?
Ferrous form (Fe2+)
77
Which form of iron binds to transferrin?
Ferric (Fe3+)
78
Which enzymes catalyses the conversion of Fe2+ to Fe3+ to enable binding to transferrin?
Copper dependent ferroxidases - primary hephaestin
79
Actions of hepcidin
- decrease dietary iron absorption - decrease iron release from liver and macrophage stores
80
Genetic mutation most commonly involved in Hereditary Haemochromatosis?
C282Y
81
Primary Biliary Cholangitis is an uncommon chronic autoimmune disorder that targets the ...
small intrahepatic bile ducts
82
Primary Sclerosing Cholangitis is a chronic inflammatory disease of the biliary tree that most commonly affects the ...
Extrahepatic bile ducts (note that can also involve intrahepatic bile ducts)
83
Gender predominance and median age of onset in PBC vs PSC
PBC - females; median age 50 years PSC - males; median age 30 years
84
What condition is associated with PSC?
Ulcerative colitis
85
What conditions are associated with PBC?
Autoimmune conditions - particularly Sjogrens syndrome and hypothyroidism
86
What is the significance of increased bilirubin in PBC?
Increased bilirubin in PBC is a late finding and indicates decompensation
87
How can Soluble Transferrin Receptor concentration be helpful in assessing for iron deficiency?
Soluble transferrin receptor concentration increases in response to iron deficiency but does not change with anaemia of chronic disease
88
Predominant raised immunoglobulin in PBC
IgM
89
Predominant raised immunoglobulin in autoimmune hepatitis
IgG
90
What are the primary bile acids?
Cholic acid Chenodeoxycholic acid
91
Markers used in FIB-4 index
Age AST ALT Platelets
92
Markers used in Hepascore
Age Sex Bilirubin GGT alpha2 macroglobulin Hyaluronic acid
93
Markers used in APRI score
AST Platelet count
94
Glycogen storage disorder associated with recurrent rhabdomyolysis and 'second wind' phenomena
McArdle Disease
95
What factors can increase alpha1 antitrypsin and mask deficiency?
Acute phase response Oestrogen
96
Causes of decreased alpha1 antitrypsin?
Pre analytical factors (e.g. delayed separation of blood with increased leucocyte esterase activity) Increased protein loss - e.g. nephrotic syndrome Decreased synthesis Genetic
97
Treatment of intrahepatic cholestasis of pregnancy?
Ursodeoxycholic acid (UDCA)
98
Main contributor to raised anion gap in methanol poisoning?
Formic acid
99
Main contributor to anion gap and metabolic acidosis in ethylene glycol poisoning?
Glycolic acid
100
Product of metabolism of ethylene glycol metabolism that can crystallise in the kidney and cause renal injury?
Oxalic acid
101
Causes of hypophosphataemia due to intracellular shifts (ECF to ICF)?
Refeeding Glucose/fructose Insulin DKA Respiratory alkalosis Alcoholism Severe burns Hungry bones
102
Major causes of Fanconi syndrome?
Cystinosis Wilson disease Multiple myeloma Heavy metal toxicity Medications (eg tenofovir)
103
What is calprotectin
Small calcium binding protein in the cytosol of neutrophils with anti-microbial activity
104
Causes of raised faecal calprotectin
GI inflammation - IBD - NSAID induced - bacterial/viral infection - microscopic colitis - diverticulities - untreated coeliac disease - colonic malignancy
105
Diagnostic criteria for acute liver failure includes:
- Hepatic encephalopathy - INR>/=1.5
106
Causes of an increased faecal osmolar gap?
Carbohydrate malabsorption syndromes (e.g. lactose, fructose) Coeliac disease Osmotic laxatives and antacids (eg, Mg, phosphate, sulfate) Sugar alcohols (e.g manitol, sorbitol)
107
What type of watery diarrhoea is defined biochemically by a low faecal osmolar gap?
Secretory
108
Calculation for faecal osmolality?
2(Na+K)
109
What does a negative faecal osmotic gap indicate?
Suggestive of phosphate or sulfate containing laxatives
110
What is the type of test used for FOBT?
Immunochemical test for human globin (iFOB uses turbidimetry)
111
Role of Faecal alpha 1 antitrypsin testing?
Faecal AAT used to **diagnose protein-losing enteropathy** (eg regional enteritis, coeliac disease, Whipple disease, intestinal lymphangiectasia); cause of unexplained hypoalbuminaemia
112
Surrogate test for fat malabsorption?
Vitamin A level
113
Causes of increased serum ACE
- Sarcoidosis - other granulomatous disease e.g. TB, leprosy - bronchitis - pulmonary fibrosis - Gauchers disease
114
Low serum ACE levels may be seen with..
Ace inhibitors Steroid therapy Some lung diseases such as bronchial carcinoma
115
Increased ACE concentration in CSF may be seen with..
Neurosarcoidosis Viral and bacterial meningitis
116
Low ACE levels in the CSF may be seen with
Alzheimers disease Parkinsons disease
117
Investigation that could be requested for ?fructose malabsorption
Breath hydrogen/methane testing
118
Enzymes located at the intestinal brush border with disaccharidase activity?
Sucrase Lactase Maltase Trehalase
119
Sites of neuroblastoma
Can occur anywhere in sympathetic nervous system * Adrenal (40%) * Abdomen (25%) * Thorax * Neck/pelvis
120
Enzyme that converts noradrenaline to adrenaline in adrenal medulla
PNMT
121
Fractions of Metanephrines
Metanephrine Normetanephrine 3-methoxytyramine (3-MT)
122
Non malignant conditions associated with increased Ca125
- Menstruation - First trimester pregnancy - Benign ovarian cysts - PID/salpingitis - Endometriosis - CCF - Pleuritis/pericarditis - Cirrhosis (due to ascites) - Renal failure - Hypothyroidism
123
Functions of Bile
* Emulsification of dietary lipids * Solubilisation of lipid digestion products * Excretion of waste products - bilirubin and cholesterol
124
Composition of Bile
* Bile Acids/Salts 70% * Phospholipids 20% * Cholesterol 5% * Bilirubin 1% * Other 4%
125
Secondary bile acids
Deoxycholic acid Lithocholic acid
126
Causes of mildly elevated amylase (<5 x ULN)
* Salivary gland disorders e.g calculi and imflammation * Chronic renal failure * Macroamylasaemia * Morphine administration (spasm of sphincter of Oddi)
127
In women, AMH is secreted by..
Pre-antral follicles (granulosa cells)
128
Classic triad of Acrodermatitis enteropathica
Alopecia Periorificial dermatitis Diarrhoea
128
Key limitations of faecal elastase in measuring pancreatic exocrine function?
* Poor sensitivity for mild disease * Falsely low results (false positives for disease) in people with diarrhoea
129
Alternate antibody testing in suspected coeliac disease
- EMA (Endomysial antibodies) - Deamidated gliadin Ab (DGLA)
129
Preferred screening test for suspected coealic disease?
Tissue transglutaminase (TTG) IgA
130
HLA types that can be tested in suspected in coeliac disease (helpful for excluding)
HLA-DQ2 HLA-DQ8
131
Conditions associated with zinc deficiency
* Vegetarian diet * Pregnancy and lactation * Exclusively breastfed infants > 6months * GI/malabsorption conditions e.g. IBD * Chronic illness * Haemoglobinopathies (sickle cell disease/thalassemia)
132
Lactose => Glucose + ____?
Galactose
133
Which sugar(s) can be used in a H2 breath test to assess for SIBO?
**Lactulose**(H2 peak earlier in gut transit time) or **Glucose** (H2 detection suggests SIBO)
134
Androgen that decreases in pregnancy
DHEAS | Due to increased metabolic clearance
135
Changes to aldosterone in pregnancy
Aldosterone increases markedly during first trimester and continues to increase to 4 – 6× URL
136
Key changes to glucose metabolism in pregnancy
- progressive insulin resistance - decrease fasting glucose
137
Components of 1st trimester screen
beta HCG PAPP-A Nuchal translucency USS
138
Components of second trimester screen
AFP uE3 Free bHCG
139
Pattern of PAPP-A and beta HCG increasing gestation (weeks 9-13 of pregnancy)
↑PAPP-A ↓hCG
140
Pattern of bHCG and PAPP-A with increasing risk in first trimester screening
↓PAPP-A ↑hCG
141
Normal trend of second trimester screening analytes with increasing gestation
↑AFP ↑uE3 ↓free beta hCG
142
A CDT level above the cut off indicates...
Excessive alcohol use >50g ethanol per day for >14 days | Can be increased in non alcoholic liver disease e.g. hepatic malignancy
143
What does PEth stand for and what does it indicate?
Phosphatidylethanol - indicates recent alcohol intake (within 2-4 weeks)
144
Sample used for PEth measurement
EDTA whole blood
145
What does EtG stand for and what does it indicate
Ethyl glucuronide - indicates recent alcohol use (within 3 days)
146
Sample used for EtG (Ethyl Glucuronide) measurement
Urine
147
Direct biomarkers of ethanol consumption
* ethyl glucuronide, * ethyl sulfate * phosphatidylethanol (PEth)
148
Indirect biomarkers of ethanol consumption
* carbohydrate deficient transferrin (CDT) * mean corpuscular volume (MCV) * liver enzymes (AST, ALT, GGT)
149
Effect of obesity on GH levels
GH levels are **lower** in obesity
150
Effects of obesity on lipids
Increase triglycerides Lower HDL
151
Chromogranin A may be elevated with NETs including..
Phaeochromocytomas GI and pancreatic endocrine tumours Carcinoid syndrome Small cell lung Ca Neuroblastoma Medullary thyroid Ca
152
Most common cause of pancreatic exocrine insufficiency in children
Cystic fibrosis
153
Pancreatic enzymes
Amylase Lipase Pepsidases - Trypsin, Chymotrypsin and Elastase
154
Causes of pancreatic exocrine insufficiency in children
* Genetic conditions (CF, others e.g. Pearson syndrome) * Development anomalies * Pancreatic resection * Chronic/recurrent pancreatitis e.g. autoimmune | Consider secondary causes of malabsorption e.g. infection, coeliac disea
155
What is a neuroendocrine tumour
Malignant growth that (sometimes) secretes bioactive peptides or amines
156
Causes of false positives for Gastrin measurement
* PPIs * Achlorhydric atrophic gastritis (withour tumours) * Conditions associated with hyperchlorhydria (e.g. H, pylori infections)
157
What does VIP stand for
Vasoactive intestinal peptide
158
Conditions associated with MEN1
* Hyperparathyroidism (95%) * Pancreatic tumours (30-80%) * Pituitary adenomas (30-40%)
159
Conditions associated with MEN2A
* Medullary thyroid carcinoma (95%) * Phaeochromocytoma (40%) * Hyperparathyroidism (10-20%)
160
Conditions associated with MEN2B
* Mucosal neuromas (99%) * Marfan body habitus (99%) * Medullary thyroid carcinoma (95%) * Phaeochromocytoma
161
What are Lights criteria for classifying pleural fluid as an exudate
*Pleural fluid-to-serum protein ratio > 0.5 *Pleural fluid-to-serum LDH ratio > 0.6 *Pleural fluid LDH greater than 0.67 (ie, two-thirds) the upper limits of the laboratory's normal serum LDH
162
'Routine' tests on pleural fluid (name 5)
*Protein *LDH *cell count *glucose *cholesterol
163
Standard B12 (total B12) assays may be low with
Pregnancy Oestrogen therapy Neutropenia Haptocorrin deficiency (rare)
164
The active form of B12 is that bound to..
Transcobalamin
165
Clinical uses of BNP (name 4)
* Diagnosis or exclusion of HF * monitoring progresion of disease & response * screening for PAH in scleroderma * cardiac amyloidosis monitoring and staging (with cardiac troponin)
166
Clinical features of chronic Lithium toxicity
o Nephrogenic DI o Primary hyperparathyroidism o Thyroid: hypothyroidism o Neurological e.g. confusion, ataxia
167
Where is procalcitonin produced?
Produced by the parafollicular cells of the thyroid and neuroendocrine cells of lung and intestine.
168
BNP is predominantly secreted from..
Left ventricle cardiac myocytes
169
Half life of BNP vs NT-proBNP
BNP 20 mins NT-proBNP 2 hours
170
Expected change in free T3 and free T4 in pregnancy
Mild decrease is seen in late pregnancy
171
For heart failure patients treated with neprilysin inhibitors, which cardiac marker is preferred?
NT-proBNP is preferred | BNP concentration has been found to increase with treatment
172
Stimulators of BNP production
* Atrial distension * Angiotensin II stimulation * Endothelin * Sympathetic stimulation
173
Time course of troponin elevation post MI
Rises by 2-3 hours post (using hsTN assay), peaks at 18-24 hours. Elevated for 10 days post AMI
174
Syndrome of apparent mineralocorticoid excess affects which enzyme
11-beta-hydroxysteroid dehydrogenase enzyme type 2 | 11-beta-HSD2 is kidney isoform. Converts cortisol ->cortisone
175
Most important test for laboratory to offer for assessment of acute porphyria?
Urine PBG | High sensitivity and specificity for current acute porphyria attack
176
Definition of microalbuminuria expressed as albumin excretion per day?
30-300mg/24 hrs
177
The laboratory definition of Tumour Lysis Syndrome is at least 2 of which 4 biochemical features?
* Hyperuricaemia * Hyperkalaemia * Hyperphosphataemia * Hypocalcaemia
178
What does ROMA stand for?
Risk of Ovarian Malignancy Algorithm
179
How is high uric acid treated in tumour lysis syndrome?
Rasburicase
180
Pre-analytical issue for patients on Rasburicase?
Continues to breakdown uric acid ex vivo -> falsely low values | Must keep cool at collection/transport, centrifuged, analysed promptly
181
Phaeochromocytomas/Paragangliomas are tumours of what cell type
chromograffin cells
182
"Classic triad" of phaeochromocytoma presentation
* episodic headach (90%) * sweating (60%) * tachycardia
183
Biomarkers for Neuroblastoma
* urine homovanillic acid (HCA) * urine vanillylmandelic acid (VMA) * chromogranin A - correlated with tumour burden and response to treatment in stage 3-4 neuroblastomas
184
Types of islet cell tumours
Insulinoma Glucagonoma Somatostatinoma Gastrinoma VIPoma
185
Medications that can cause low Mg due to renal losses
* Diuretics - loop and thiazide * Antibiotics e.g. aminoglycosides * Cisplatin * Antibodies targetin EGF receptor (e.g. cetuximab) * Calcineurin inhibitors
186
Which type of porphyria typically occurs in childhood?
Erythryopoietic Protoporphyria (EPP)
187
Types of Acute Porphyrias
* ALA dehydratase deficiency (ADP) * Acute intermittent porphyria (AIP) * Hereditary coproporphyria (HCP) * Variegate porphyria (VP)
188
Types of Non-Acute Porphyrias
* X-linked dominant protoporphyria (XLDPP) * Congenital erythropoietic porphyria (CEP) * Porphyria Cutaenea Tarda (PCT) * Erythropoeitic Protoporphyria (EPP)
189
Most common type of renal stone
Calcium oxalate
190
Types of renal stone
- Calcium oxalate – most common - Mixed calcium oxalate - phosphate - Calcium phosphate (8%) - Uric acid (8%) - Struvite (Mg ammonium phosphate) 12% - Cysteine (1-2%)
191
What is Homocysteine
Intermediary amino acid formed by the conversion of methionine to cysteine
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Classical homocystinuria results from deficiency in which enzyme
Cystathionine beta-synthase (CBS)
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Clinical features of Homocystinuria
* Developmental delay * Marfanoid appearance * Osteoporosis * Ocular abnormalities * Thromboembolic disease * Severe premature atherosclerosis
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The transsulfuration of homocysteine to cysteine by CBS requires ____ as a cofactor
Pyridoxal phosphate (vitamin B6)
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What does urine PBG stand for?
Urine Porphobilinogen
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Causes of raised urine porphyrins
* Porphyria Secondary porphyrias (mainly coproporphyrin) * Cholestatic liver disease * Lead poisoning * Heavy metals (gold, arsenic) * some haematological disorders
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A peak at 626nm on plasma fluorescence is a hallmark of which type of porphyria?
Variegate Porphyria
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On HPLC Faecal profiling for porphyrias, which is the hallmark compound of PCT?
Isocoproporphyrin
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Causes of hypophysitis
* Lymphocytic hypophysitis (most common) * Complication of immunotherapy (e.g. ipilimumab) * Granulomatous * IgG4-associated
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Causes of increased serum total bile acids
* Intrhepatic cholestasis of pregnancy * Acute hepatitis * Chronic hepatitis * Liver sclerosis * Liver malignancy
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If no clear cause of increased serum uric acid on initial assessment, what further test could be performed?
Fractional urinary excretion of uric acid
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Biochemical features of refeeding syndrome
Hyperinsulinism Hypophosphataemia Hypokalaemia Hypomagnesaemia Low thiamine
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Biochemical features of Tumour Lysis Syndrome
Hyperphosphataemia Hyperkalaemia High LDH Hyperuricaemia Hypocalcaemia
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Impacts of Amiodarone on TFTs
- reduced T4 to T3 conversion - Transient increase TSH with treatment commencement - Thyrotoxicosis - Hypothyroidism (failure to escape Wolff-Chaikoff effect)
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Adverse effects on the endocrine system of immune checkpoint blockade
- Thyroid disease - Hypophysitis - Adrenal insufficiency - Insulin deficient DM - Hypoparathyroidism
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Types of ALP isoenzymes
* Tissue non specific (Bone, Liver, Kidney) * Intestinal ALP * Placental ALP * Germ cell ALP ("Placental like ALP")
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A copeptin measurement of >4.9 can help exclude..
AVP deficiency
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The kidney removes acid by 3 main mechanisms:
1. Excretion of "titratable acids" 2. Reabsorption of bicarbonate 3. Excretion of ammonium (generation of bicarbonate)
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What are "titratable acids" excreted in urine
* **Phosphate** * Citrate * Urate * Hippurate | Group of conjugate bases acting as buffers.
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Most (70-80%) of the filtered bicarbonate in the kidney is reabsorbed in the ...
Proximal tubules | Most of the remainder is reabsorbed via the thick ascending limb
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Main mechanism in kidney which increases in response to significant acid load
Increased ammonium excretion
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Type 1 RTA affects the ...
Distal tubules. | Impaired urinary proton excretion
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Causes of Type 1 RTA
1. Primary - Genetic mutations 2. Secondary - Autoimmune disorders (including Sjogrens syndrome) - Drugs e.g. Amphotericin B - Hypercalciuric conditions
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Biochemical Picture of Type 1 RTA
* NAGMA * Hypokalaemia * Urine pH > 5.5 * Low urine ammonium * Low urine bicarbonate * Hypercalciuria (renal stones common)
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Type 2 RTA affects the ..
Proximal tubules | Impaired bicarbonate reabsorption
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Biochemical features of Fanconi syndrome
Hypophosphataemia Hyperphosphaturia Glycosuria Proteinuria and aminoaciduria
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Biochemical Picture of Type 2 RTA
* NAGMA * high urine bicarbonate * hypokalaemia * low urine pH * elevated urinary ammonium
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Biochemical picture of Type 4 RTA
* NAGMA (mild if present) * Hyperkalaemia * appropriately low urine pH (<5.5) * low urine ammonium * low urine bicarbonate
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Elevated fractional excretion of bicarbonate is diagnostic of which type of RTA?
Type 2 RTA
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Proxy measurement of urine NH4+
Urine anion gap
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Functional deficiency of aldosterone is what type of RTA?
Type 4
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Calculation of urine anion gap
Na + K - Cl
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In a type 1 RTA (distal tubular defect), the urinary anion gap will be ..
Positive
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Causes of marked increase in bone remodelling
* Pagets disease * Hyperthyroidism * Malignancy * Late offset of Denosumab
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Negative acute phase reactants (name 6)
* Albumin * Pre-albumin * Transferrin * AFP * IGF-1 * TBG
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Positive acute phase reactants
* Complement system - C3, C4 * Fibrinogen; Plasminogen * Haptoglobin * Anti-proteases * Caeuruloplasmin * CRP
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A negative urine anion gap (-20 or less) indicates..
Increased ammonium excretion. Occurs in patients with metabolic acidosis secondary to diarrhoea
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Urine anion gap can be unreliable in measuring NH4+ in the setting of "unmeasured" anions such as...
Ketones Hippurate (toluene inhalation) | UAG not reduced as occurs when ammonium is excreted with chloride
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Urine osmolar gap of <150 in a patient with chronic metabolic acidosis is suggestive of
Type 1 or type 4 RTA
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An intrauterine pregnancy should be visible when the hCG is at what level?
1500 - 2000 IU/L
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Type of Cryoglobulin associated with monoclonal immunoglobulin
Type 1
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Type of cryoglobulin composed of a mixture of a monoclonal IgM (or IgG or Iga) with RF activity and polyclonal IgG
Type 2 | Often associated with Hep C; Autoimmune diseases - SLE, Sgorens
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Type of cryoglobulins composed of mixture of polyclonal IgG and polyclonal IgM
Type 3 | Often secondary to autoimmune disorders
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Causes of low SHBG
* Obesity * Insulin resistance * PCOS * Hypothyroidism * Nephrotic syndrome * Prolactin, androgen, corticosteroid or GH increase
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Patients that form Lipoprotein X
* cholestatic liver disease * mutations or deficiencies in LCAT | LCAT = Lecithin-Cholesterol Acyltransferase. Esterifies cholesterol.
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What is lipoprotein X composed of
Phospholipids, free cholesterol, ApoA1, Albumin | Lacks ApoB100
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Principal role of chylomicrons
Delivery of dietary lipids to hepatic and peripheral cells
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Principal role of VLDL
Major carriers of endogenous (hepatic derived) TGs | Shuttle TGs from liver to peripheral tissue
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Lipoproteins that contain ApoB100
LDL, Lipoprotein(a), IDL, VLDL
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Lipoproteins that contain ApoE
CM VLDL IDL | ApoE binds remnant receptors (liver)
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Causes of chylous effusions
* Surgery * Malignancy (lymphoma) * Lymphatic malformations
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Causes of pseudo chylous effusions
Rheumatoid pleurisy Tuberculosis
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Presence of bilirubin in the CSF indicates Hb has been in the CSF for how long
12 hrs to 2 weeks
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2 tests to identify CSF:
- beta-2 transferrin (tau protein) - beta trace protein
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Normal pattern for CSF for - glucose - protein - chloride
* glucose about half plasma * very low protein (<0.4g/L) * chloride about 5-10mmol/L higher than plasma
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Markers of Alzheimers disease in CSF
* Abeta 1-42 decrease * P-tau increase * Ratio of P-tau: Abeta 1-42 increased
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Causes (mechanisms) of increased L-Lactate
1. Defect in pyruvate oxidation (tissue hypoxia or defect in TCA cycle; mitochondrial resp chain) 2. Defect in rate limiting enzymes of glycolysis 3. Excess cytosolic NADH
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Do laboratory methods detect D-lactate
No. L-LO and L-LDH is used in the assays
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The main ketone that starts to increase after fasting 12-14 hours is
Beta- hydroxybutyrate
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Biochemical changes in DKA (on K, P, Na, Cr)
* Initial hyperkalaemia * Hyperphosphataemia (low after treatment) * Hyponatreamia * Falsely elevated Cr using Haffe method (interference from ketones)
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Flucloxacilin and paracetamol can result in a HAGMA due to accumulation of...
5- oxoproline (Pyrogluamic acid)
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Inherited causes of increased triglycerides
* Familial hyperchylomicronaemia (type 1) - e.g. lipoprotein lipase deficiency * Familial dysbetalipoproteinaemia (type 3)- ApoE2 * Familial combined hyperlipoproteinaemia - polygenic * Primary hypertriglyceridaemia (type 4) - unknown genetics
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Secondary causes of increased TG
- Diabetes mellitus - Obesity - MAFLD - Alcohol excess - Nephrotic syndrome (chol more affected) - Pregnancy - Medications: Glucocorticoids, Oestrogen, Diuretics (e.g. chlorothiazide)
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What does PKU stand for
Phenylketonuria
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Classic PKU affects which enzyme
Phenylalanine Hydroxylase | Affects conversion of phenylalanine to Tyrosine
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What calculation may be used to further assess hyper or hypokalaemia?
Transtubular potassium gradient (TTKG) | Estimates the degree of renal potassium excretion in the distal nephron
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During hyperkalaemia, the TTKG should be ...
Greater than 7 | Lower values suggest hypoaldosteronism
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During hypokalaemia, the TTKG should be..
Less than 3 | Greater values suggest renal potassium wasting
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Measures needed to calculate TTKG
* Urine K * Urine osmolality * Plasma osmolality * Plasma K
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Causes of increased LDH
* MI * Pneumonia * CCF * hepatic injury * Haemolysis * Ineffective haematopoesis * Skeletal muscle injury * Renal injury * Pancreatitis * Tumour - especially testicular or lymphoma
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hCG can be used as a tumour marker in which malignancies
* Germ cell tumours (Germinomas; Choriocarcinomas) * Gestational trophoblastic disease
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Name 5 bone formation markers
* ALP - Alkaline phosphatase * Bone specific ALP * P1NP - Procollagen Type 1 N propeptide * P1CP - Procollagen Type 1 C propeptide * Osteocalcin
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Name 5 bone resorption markers
* CTX - Carboxy-terminal crosslinking telopeptide of type 1 collagen * NTX - Amino-terminal crosslinking peptide of type 1 collagen * DPD - Deoxypyridinoline * PYP - Pyridinoline * TRACP - Serum tartrate-resistant acid phosphatase
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Limitations of BTMs
* Reflect total skeletal turnover * Not always specific to bone metabolism * Substantial biological variability * Multiple assays for same analyte * Do not assess osteocyte activity
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Main sites of cortical bone in the body
Skull and long bones
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Main sites of trabecular bone in the body
Vertebrae Ribs Distal ends of long bones
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Biochemical profile of Acute Fatty Liver of Pregnancy (Swansea criteria)
* Elevated total bilirubin * elevated AST or ALT * hyperammonaemia * elevated urate * hypoglycaemia * AKI * coagulopathy * Leukocytosis
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Changes to binding globulins in pregnancy
Increase TBG, CBG, SHBG
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Changes to glucose in pregnancy
BSL lower approx 20% | Increase in insulin
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Changes to calcium in pregnancy
* total calcium lower due to lower albumin * free/ionised calcium stable * increase 1,25(OH) vit D - palcental. Increased GIT absorption. * Hypercalciuric mother * Maternal PTH decreases first half pregnancy * PTHrP - ca across placenta to fetus
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Changes to Cr in pregnancy
Decreases 20-30mmol/L (increase in GFR)
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Changes to Free T4/T3 in pregnancy
Decreases late pregnancy
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Aldo and renin changes in pregnancy
Increase aldosterone by 8 weeks Increase renin and aldosterone mostly by 3rd trimester
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Changes to androgens in pregnancy
Increase Except for DHEAS which decreases
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What is a neuroendocrine tumour
A malignant growth that (sometimes) secretes bioactive peptides or amines
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Clinical use of CRH Stimulation Testing
May be combined with IPSS in diagnosing Cushing disease - Measure ACTH and cortisol post CRH injection | Significant rise in ACTH or cortisol from baseline- suggests pituitary
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Contraindications for Clonidine suppression test
Clonidine can cause hypotension and is contraindicated in frail patients with a history of hypotensive episodes/ severe coronary/ carotid disease
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How to interpret clonidine suppression test
Abnormal test result (indicating a PPGL) includes: - an elevation of plasma normetanephrine at 3 h after clonidine administration - <40% decrease in levels compared with baseline
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Medications that can interfere with clonidine suppression test
* Beta blockers - avoid for 48 hours prior * Paracetamol, diuretics, TCAs - at least.5 days * Caffeine, smoking - avoid for 24 hours
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What is exercise growth hormone testing used to investigate?
Suspected GH deficiency
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What is Glucagon stimulation test used for?
Suspected GH deficiency
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Interpretation of Glucagon stimulation test:
Normal response is any GH > 3ug/L | Cut off based on lean subjects. Lower GH response in obesity group.
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Effects of glucagon
Stimulates glycogenolysis in the liver Stimulates GH and ACTH release form the pituitary
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Risk associated with performing Glucagon stimulation test
Risk of late hypoglcycaemia
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Interpretation of IPSS
A central to peripheral ACTH ratio of ≥ 2 pre CRH and / or a ratio of ≥ 3 post CRH is consistent with Cushing’s disease
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With an IPSS, If the central to peripheral ACTH ratios are not elevated on either side, what does this indicate?
* may have ectopic source of ACTH or * petrosal sinus was not succesfully cannulated | Petrosal sinus/peripheral prolactin ratio >1.8 - adequate cannulation
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What is struvite
Magnesium ammonium phosphate
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Causes of hyperoxaluria
- usually acquired e.g. compromised ileal function; low calcium intake - primary hyperoxaluria is rare | Calcium binds oxalate and prevents absorption
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Analytes to measure in urine for investigation of renal stones
- Calcium - oxalate - urate - cysteine - citrate
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Causes of hypocitraturia
Most commonly acidosis or acid retention - distal renal tubular acidosis - metabolic acidosis of chronic diarrhoea - lactic acidosis from physical exercise Can also occur with UTIs
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Contraindications to OGTT
History of bariatric surgery | Increased risk of hypoglycaemia
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Serum glucose levels in keeping with DM
Fasting >/=7.0 Random or 2 hour >/=11.1
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Normal cut offs for OGTT (non pregnant)
Fasting
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Cut offs for pregnacy OGTT
Fasting <5.1 1 hr <10 2 hr <8.5
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Cut off for normal response in oral glucose suppression test for GH excess
Normal response is GH <1.0ug/L at any timepoint
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Causes of false positives in oral glucose suppression test for GH excess
* Poorly controlled DM * Nutritional disorders (e.g. anorexia nervosa) * Renal disease * Liver failure | Associated with acquired GH insensitivity to glucose suppression
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Causes of false positives for low dose Dexamethasone suppression test
* Non compliance * Malabsorption * Drugs inducing the hepatic metabolism of dex (e.g. carbamazepine, phenytoin) * Drugs elevating CBG (oestrogens) * CKD
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How to interpret high dose dexamethasone suppression test
Decrease in serum cortisol >50% is suggestive of pituitary Cushing disease (rather than ectopic ACTH) | However sensitivity and specificity approx 80%
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Why is a late night salivary cortisol performed before an IPSS?
To confirm if in active phase of hypercortisolism | False results can occur in patients not in active phase when tested
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Role of bone ALP in CKD MBD
* high results predict # * high results can help exclude adynamic bone disease
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Effect of Romosozumab on bone turnover markers
* Initial increase in P1NP then return to baseline * Decrease CTX
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Effect of teriperatide on bone turnover markers
* Increase in P1NP * Increase in CTX | Intermittent PTH -> increases Wnt signalling, promotes bone formation
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Type of bone affected with prolonged elevated PTH
Cortical > trabecular bone loss
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What level of copeptin indicates complete central DI
Copeptin <2.6pmol/L WITH prior fluid deprivation (>8 hours)
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What level of copeptin indicates nephrogenic DI
Copeptin >21.4pmol/L WITHOUT prior fluid deprivation
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Intrepretation of TRH Stimulation test
TSH-oma: TSH rarely increases following TRH Thyroid hormone resistance - > 4 fold increase in serum TSH
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How to differentiate TSHoma and thyroid hormone resistance
* SHBG and CTX are elevated in hyperthyroidism (TSHoma) * Alpha subunit elevated in 70% TSH-oma (not helpful in post menopausal women) * TFT testing in 1st degree relatives if available * THRB gene test - thyroid hormone resistance
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How do ammonia levels in infants compare to adults?
Higher levels in infants, especially pre-term infants
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Endocrine effects of Lithium
* Thyroid - inhibits release of T4/T3 - hypothyroidism (or subclinical hypothyroidism) * PTH - higher set point for calcium; parathyroid hyperplasia; can worsen PHPT * Renal - Nephrogenic DI
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Examples of Anti-TNF agents used in treatment of autoimmune conditions (e.g. IBD)
* Infliximab * Adalimumab (Humira)
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Lack of lateralisation with an AVS test can occur with:
* Bilateral aldosterone producing adenoma * Bilateral adrenal hyperplasia * Glucocorticoid Remediable Aldosteronism
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Changes to prolactin with GAHT
- Prolactin increases with E2 - Decreases or unchanged with testosterone
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Features differentiating MGUS from MM
* Clonal BM plasma cells <10% in MGUS * M protein <30g/L in MGUS (any level in MM) * Absence of CRAB SLiM criteria | CRAB SLiM crtiteria includes involved/uninvolved serum FLC ratio >100
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Phaeochromocytomas tend to produce..
Both Noradrenaline and Adrenaline
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Paragangliomas tend to produce..
Noradrenaline
317
What is the enzyme that converts Norepinephrine to Epinephrine and where is it located
PNMT Expressed in the adrenal medulla | Not expressed in sympathaetic neurons
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Catecholamines includes
* Adrenaline * Noradrenaline * Dopamine
319
Metanephrtines (metabolites of catecholamines) includes
* Metanephrine * Normetanephrine * 3-Methyoxytyramine (3MT)
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Tests for medullary thyroid carcinoma
* Calcitonin * CEA * Genetic testing - RET mutations * Testing for coexisting tumours - Ca/PTH, plasma free metanephrines
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Clinical causes of increased TMP/GFR
* Thyroxine * GH/IGF-1 * Hypoparathyroidism * Insulin * Etidronate (bisphosphonate) * Catecholamine * Calcitriol * After unilateral ureteric obstruction
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Intestinal absorption of phosphate is via the .. transporter
NAPT IIb | Dependent on 1,25(OH)D
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Non pathological causes of short stature
* Ethnic short stature * Familial short stature * Constitutional growth delay
324
GH Stimulation Test can use..
* Exercise * Glucagon * Arginine * Clonidine
325
Endocrine causes of short stature
* GH deficiency or receptor defector * Hypthyroidism * T1DM - poorly controlled * Cushings
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PSA in serum is mostly bound to...
Alpha-1-antichymotrypsin
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Functional role of PSA
Present in seminal fluid in high concentrations. Cleaves the high molecular mass simnal vesicle protein Semenogelin
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Whcih has greater cardiac specificity - cTnI or cTnT?
cTnI | Raised cTnT but normal cTnI in some pts with skeletal muscle disease
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Differentials for increased urine porphyrins but with normal faecal porphyrins
* Liver disease * Medications * Lead poisoning
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Causes of increased serum beta 2 microglobulin
* Haematological disorders e.g. leukaemia, lymphoma, myeloma* * Viral infections - Hepatitis * CT disorders - SLE * IBD * Solid malignancy - e.g. hepatoma * Hyperthyroidism * Renal impairment | *Used in staging of Multiple Myeloma
331
Name of criteria used for Tumour Lysis Syndrome
Cairo-Bishop criteria
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Definition (criteria) of laboratory tumour lysis syndrome
≥2 key metabolic features that present within three days before or seven days after instituting chemotherapy: * Hyperkalaemia - >6mmol/L or increase 25% from baseline * Uric acid - increase 25% from baseline * Hyperphosphataemia - or increase 25% from baseline * Hypocalcaemia - <1.75mmol/L or decrease 25% from baseline
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Definition (criteria) of Clinical Tumour Lysis Syndrome
Clinical TLS – Laboratory TLS plus ≥1 of the following findings that are not directly or probably attributable to a therapeutic agent: * increased serum creatinine concentration (≥1.5 times the upper limit of normal), * cardiac arrhythmia/sudden death, or * seizure.
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What is the most common type of gall stone in Western society
Cholesterol galls stones (cholesterol >50%) Remainder are pigment stone
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What is a "peritoneal mouse"
Description for asymptomatic incidentaloma found at surgery. Evolve from torsion and separation of the appendices epiploicae
336
In PHPT, what type of bone is preferentially lost?
Cortical bone
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What urine feature is characteristic of uric acid stone formation?
The urine is characteristically abnormally acidic. Additional findings may include hyperuricuria and low urinary output.
338
Effects of glucocorticoid on thyroid function
- suppression of TSH secretion - impaired conversion T4 -> T3
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Drugs that suppress TSH secretion?
- Glucocorticoids - Octreotide - Dobutamine
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Medications associated with isolated reduction in T4
* salicylate * oestrogen * carbamazepine
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hCG used as tumour marked in which malignancies
- gestational trophoblastic disease - germ cell tumours: germinomas; or non-germinomatous (**choriocarcinoma**, embryonal carcinoma, mixed germ cell)
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Main role of A1AT
Inhibition of proteases including neutrophil derived elastase
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Clinical condition which causes black urine
Alkaptonuria
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What is alkaptonuria
Inherited disorder affecting the enzyme HGO -> accumulation of homogentisic acid
345
What does PAPP-A stand for
Pregnancy associated plasma protein A
346
What does GAD (antibodies) stand for?
Glutamic acid decarboxylase
347
Name of the diagnostic criteria used for Multiple sclerosis
McDonald criteria
348
A doctor has requested PCT. What does it stand for?
Procalcitonin
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What is DIDMOAD syndrome and what does the acronym stand for?
Wolfram syndrome: Diabetes insipidus Diabetes mellitus Optic atrophy Deafness
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What does AIP stand for?
Acute Intermittent Porphyria
351
What does the condition SSPE stand for?
Subacute sclerosing panencephalitis
352
What is the name of the syndrome characterised by development of hyperthyroidism following idoine supplementation?
Jod-Basedow syndrome
353
What is the definition of proteinuria in assessment of pre-eclampsia?
>300mg of protein in 24 hour urine collection
354
What does sFLT-1 stand for?
soluble FMS like tyrosine kinase-1
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What does ICP stand for?
Intrahepatic Cholestasis of Pregnancy
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What does HE4 stand for?
Human Epididymis protein 4 | Tumour marker ovarian cancer
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Components of ROMA
* Ca125 * HE4 * menopausal status
358
Calculating contribution of ethanol level on serum osmolality
* Calculate blood alcohol % as mg/dL (x1000) * Convert mg/dL to mmol/L by dividing by 4.61 * Ethanol level (in mmol/L) * 1.25 for calculated osmolality
359
Classic triad of phaeochromocytoma
* Headaches * Palpitations * Sweating