Clinical Flashcards
Causes of primary ovarian insufficiency (POI)
- Idiopathic
- Turner syndrome
- Premutations for Fragile X
- Autoimmune (may be part of polyglandular syndrome)
- Toxicity to ovaries - chemoTx, RadioTx
Physiological stimulators of GH secretion
Hypoglycaemia
Fasting
Starvation
Exercise
Stress and trauma
Sepsis
Insulin
GH secretion is inhibited by..
Hyperglycaemia
Increase in free fatty acids in blood
Hereditary causes of methaemoglobinaemia?
HbM
Cytochrome b5 reductase deficiency
G6PD deficiency (however minor role compared to cytochrome b5 reductase)
Acquired causes of methaemoglobinaemia?
Medications e.g. Benzocaine; dapsone; primaquine
Chemical agents e.g. chlorobenzene; silver nitrate
Nitrate containing foods
What clinical signs/findings lead to a diagnosis of methaemoglobinaemia?
Cyanosis unresponsive to oxygen
Chocolate coloured blood
Saturation gap of >5% (difference between pulse oximeter and multiwavelength oximeter)
Methods to confirm presence of increased Met-Hb?
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)
What factors other than GnRH regulate FSH secretion?
- Inhibin - inhibits FSH secretion
- Activin - activates FSH secretion
Causes of decreased IGF-1
- GH deficiency
- Malnutrition
- Liver failure
- Renal failure
- Hypothyroidism
- Poorly controlled DM
- Severe infection
Differentials for neonatal jaundice - predominantly conjugated
- 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)
Causes of hypopituitarism
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
Typical order of affected hormones with hypopituitarism
- Hypogonadism
- GH deficiency
- ACTH
- Hypothyroidism
- Prolactin - rarely deficient
With what causes of hypopituitarism is ACTH secretion more likely to be affected? (name 2)
Lymphocytic hypophysitis
Immune checkpoint inhibitors
What does MELAS stand for?
Mitochondrial
Encephalomyopathy with
Lactic
Acidosis and
Stroke-like episodes
What does LHON stand for?
Leber
Hereditary
Optic
Neuropathy
What happens to SHBG in TSHoma vs thyroid hormone resistance?
Elevated in TSHoma
Normal in thyroid hormone resistance
What happens to alpha subunit in TSHoma?
Elevated alpha subunit: TSH ratio
Tumours associated with MEN1?
- Parathyroid
- Pituitary adenomas (e.g. prolactin; non-functioning; acromegaly)
- Pancreas (e.g. non functioning; gastrinoma; insulinoma)
What proportion of Familial isolated hyperparathyroidism have MEN1 mutation?
20%
What gene is affected in MEN2?
RET (oncogene)
What gene is affected in Wilsons disease?
ATP7B gene - affects the function of the ATPase2 membrane protein
What does POMC stand for?
Pro-opio-melanocortin
What hormones are produced by the corpus luteum?
Steroids: E2, progesterone
Non steroids: Relaxin, VEGF
What are the criteria for successful cannulation with AVS?
Adrenal vein cortisol/Peripheral vein cortisol
>/=2 at baseline
>/=3 post ACTH stimulation
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
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
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
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
Causes of increased DHEAS
- CAH
- Cushings
- Adrenal tumour
- PCOS
Causes of transiently elevated prolactin
- Recent seizure
- Drug related
- Breast feeding
- Post coital elevation
- Rarely Pituitary apoplexy
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
A bilateral total adrenalectomy in association with
ACTH-dependant Cushing’s may result in which syndrome?
Nelson syndrome
Causes of central diabetes insipidus?
Pituitary tumour
Neurosurgery
Head trauma
Causes of nephrogenic DI?
Lithium
Renal Dx
Hypokalaemia
Pregnancy
What is the cofactor for AST and ALT?
Pyridoxal-5-phosphate
What are 2 confounding factors in interpreting the level of plasma P5P
Albumin (plasma P5P is bound to albumin)
ALP (degrades P5P)
Risk factors for P5P deficiency?
Elderly
Alcoholism
Coeliac disease
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)
What are the half lives of ALT and AST?
ALT 36hrs
AST 18hrs
What is the half life of CK?
12hrs
What is the half life of albumin?
15-19 days
Causes of increased loss of albumin?
Nephrotic syndrome
Severe blood loss
Burns
Causes of low albumin relating to increased metabolism?
Sepsis
Burns
Malignancy
Hyperthyroidism
What happens to albumin in inflammation?
Reduced concentration due to decreased synthesis (inhibition by IL-6 , TNF)
What does SAAG stand for?
Serum ascites albumin gradient
What does SAAG of 11 or above indicate?
Ascites secondary to portal hypertension (e.g. CCF, cirrhosis, alcoholic hepatitis)
What does SAAG < 11 indicate?
Ascites not associated with portal hypertension (e.g. nephrotic syndrome, pancreatitis, peritoneal carcinoma, TB)
What is the Payne formula for corrected calcium?
Corrected calcium = Total calcium + 0.02 x (40 - Albumin)
What is the toxic metabolite that increases in paracetamol overdose and causes hepatic necrosis?
NAPQI (N-acetyl-p-benzoquinoneimine)
Causes of increased intestinal ALP?
Blood groups O and B - especially after a fatty meal
Cirrhosis
T2DM
Inflammatory bowel disease
Causes of low ALP
Pre-analytical - EDTA or citrate contamination
Hypophosphatasia
Zn and Mg deficiency
Untreated hypothyroidism
Bisphosphonates
Wilson disease
What can be used to separate bone and liver ALP on gel electrophoresis?
Neuraminidase
(other option is Lectin)
Biochemical findings in hypophosphatasia?
↓ALP
↑B6 in serum
↑ PEA in urine
What reduces NAPQI to nontoxic mercaptate and cysteine compounds for renal excretion?
Glutathione
Name 2 prognostic scoring systems for severe liver disease?
Child-Turcotte-Pugh
MELD (Model for End-stage Liver Disease)
Causes of decreased albumin
- Inflammation
- Decreased production (severe liver disease)
- Increased loss (e.g. nephrotic syndrome)
- Haemodilution (e.g. pregnancy)
Formula for “R ratio” of LFTs
(ALT/ALT URL)/(ALP/ALP URL)
What does a LFT “R ratio” of >5 indicate?
Hepatocellular damage
What does a LFT “R ratio” of <2 indicate
Cholestasis
Name the 4 types of ALP isoenzymes
- Tissue non specific (Liver/Bone/Kidney)
- Intestinal
- Germ cell
- Placental
Medications that can cause a false positive ARR due to reduced renin
Beta blockers
Methyldopa
Clonidine
NSAIDs
OCP
What medications can give false negatives of ARR?
ACE inhibitors
Angiotensin II receptor antagonists
Calcium channel blockers (Dihydropyridines)
Diuretics
Spironolactone
What is the impact of posture on aldosterone and renin?
Increase with standing (more pronounced increased for renin)
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
What is the potential impact of the luteal phase on ARR?
False positives are more likely in luteal phase
(Increase aldosterone and decrease renin)
Classic biochemical findings in salicyclate toxicity?
Respiratory alkalosis (hyperventilation) followed by metabolic acidosis (due to accumulation of organic acids)
Hypoglycaemia
Hypokalaemia, Hypercalcaemia
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
Differentials for HELLP syndrome
Pre-eclampsia
Acute Fatty Liver of Pregnancy
Biochemical profile of Acute Fatty Liver in Pregnancy (Swansea criteria)
Elevated total bilirubin
Elevated AST or ALT
Elevated Urate
AKI
Coagulopathy
Hyperammonaemia
Hypoglycaemia
Presenting symptoms of Obstetric Cholestatis
Occurs 2nd half of pregnancy
Pruritus
RUQ pain
Nausea
Steatorrhoea
Jaundice
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
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
Which inherited disorder has been associated with acute fatty liver in pregnancy?
Fetal long-chain 3-hydroxyacyl CoA dehydrogenase (LCHAD) deficiency
Clinical Features of obstetric cholestasis
Occurs 2nd half of pregnancy
Pruritus
RUQ pain
Nausea
Steatorrhoea
Jaundice
Biochemical profile of Obstetric Cholestasis
Elevated bile acids (cholic acid; Chenodeoxycholic acid)
Elevated bilirubin
AST, ALT mild rise
ALP/GGT increased
Which form of iron is taken up by DMT1 in the duodenum?
Ferrous form (Fe2+)
Which form of iron binds to transferrin?
Ferric (Fe3+)
Which enzymes catalyses the conversion of Fe2+ to Fe3+ to enable binding to transferrin?
Copper dependent ferroxidases - primary hephaestin
Actions of hepcidin
- decrease dietary iron absorption
- decrease iron release from liver and macrophage stores
Genetic mutation most commonly involved in Hereditary Haemochromatosis?
C282Y
Primary Biliary Cholangitis is an uncommon chronic autoimmune disorder that targets the …
small intrahepatic bile ducts
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)
Gender predominance and median age of onset in PBC vs PSC
PBC - females; median age 50 years
PSC - males; median age 30 years
What condition is associated with PSC?
Ulcerative colitis
What conditions are associated with PBC?
Autoimmune conditions - particularly Sjogrens syndrome and hypothyroidism
What is the significance of increased bilirubin in PBC?
Increased bilirubin in PBC is a late finding and indicates decompensation
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
Predominant raised immunoglobulin in PBC
IgM
Predominant raised immunoglobulin in autoimmune hepatitis
IgG
What are the primary bile acids?
Cholic acid
Chenodeoxycholic acid
Markers used in FIB-4 index
Age
AST
ALT
Platelets
Markers used in Hepascore
Age
Sex
Bilirubin
GGT
alpha2 macroglobulin
Hyaluronic acid
Markers used in APRI score
AST
Platelet count
Glycogen storage disorder associated with recurrent rhabdomyolysis and ‘second wind’ phenomena
McArdle Disease
What factors can increase alpha1 antitrypsin and mask deficiency?
Acute phase response
Oestrogen
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
Treatment of intrahepatic cholestasis of pregnancy?
Ursodeoxycholic acid (UDCA)
Main contributor to raised anion gap in methanol poisoning?
Formic acid
Main contributor to anion gap and metabolic acidosis in ethylene glycol poisoning?
Glycolic acid
Product of metabolism of ethylene glycol metabolism that can crystallise in the kidney and cause renal injury?
Oxalic acid
Causes of hypophosphataemia due to intracellular shifts (ECF to ICF)?
Refeeding
Glucose/fructose
Insulin
DKA
Respiratory alkalosis
Alcoholism
Severe burns
Hungry bones
Major causes of Fanconi syndrome?
Cystinosis
Wilson disease
Multiple myeloma
Heavy metal toxicity
Medications (eg tenofovir)
What is calprotectin
Small calcium binding protein in the cytosol of neutrophils with anti-microbial activity
Causes of raised faecal calprotectin
GI inflammation
- IBD
- NSAID induced
- bacterial/viral infection
- microscopic colitis
- diverticulities
- untreated coeliac disease
- colonic malignancy
Diagnostic criteria for acute liver failure includes:
- Hepatic encephalopathy
- INR>/=1.5
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)
What type of watery diarrhoea is defined biochemically by a low faecal osmolar gap?
Secretory
Calculation for faecal osmolality?
2(Na+K)
What does a negative faecal osmotic gap indicate?
Suggestive of phosphate or sulfate containing laxatives
What is the type of test used for FOBT?
Immunochemical test for human globin
(iFOB uses turbidimetry)
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
Surrogate test for fat malabsorption?
Vitamin A level
Causes of increased serum ACE
- Sarcoidosis
- other granulomatous disease e.g. TB, leprosy
- bronchitis
- pulmonary fibrosis
- Gauchers disease
Low serum ACE levels may be seen with..
Ace inhibitors
Steroid therapy
Some lung diseases such as bronchial carcinoma
Increased ACE concentration in CSF may be seen with..
Neurosarcoidosis
Viral and bacterial meningitis
Low ACE levels in the CSF may be seen with
Alzheimers disease
Parkinsons disease
Investigation that could be requested for ?fructose malabsorption
Breath hydrogen/methane testing
Enzymes located at the intestinal brush border with disaccharidase activity?
Sucrase
Lactase
Maltase
Trehalase
Sites of neuroblastoma
Can occur anywhere in sympathetic nervous system
* Adrenal (40%)
* Abdomen (25%)
* Thorax
* Neck/pelvis
Enzyme that converts noradrenaline to adrenaline in adrenal medulla
PNMT
Fractions of Metanephrines
Metanephrine
Normetanephrine
3-methoxytyramine (3-MT)
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
Functions of Bile
- Emulsification of dietary lipids
- Solubilisation of lipid digestion products
- Excretion of waste products - bilirubin and cholesterol
Composition of Bile
- Bile Acids/Salts 70%
- Phospholipids 20%
- Cholesterol 5%
- Bilirubin 1%
- Other 4%
Secondary bile acids
Deoxycholic acid
Lithocholic acid
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)
In women, AMH is secreted by..
Pre-antral follicles (granulosa cells)
Classic triad of Acrodermatitis enteropathica
Alopecia
Periorificial dermatitis
Diarrhoea
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
Alternate antibody testing in suspected coeliac disease
- EMA (Endomysial antibodies)
- Deamidated gliadin Ab (DGLA)
Preferred screening test for suspected coealic disease?
Tissue transglutaminase (TTG) IgA
HLA types that can be tested in suspected in coeliac disease (helpful for excluding)
HLA-DQ2
HLA-DQ8
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)
Lactose => Glucose + ____?
Galactose
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)
Androgen that decreases in pregnancy
DHEAS
Due to increased metabolic clearance
Changes to aldosterone in pregnancy
Aldosterone increases markedly during first trimester and continues to increase to 4 – 6×
URL
Key changes to glucose metabolism in pregnancy
- progressive insulin resistance
- decrease fasting glucose
Components of 1st trimester screen
beta HCG
PAPP-A
Nuchal translucency USS
Components of second trimester screen
AFP
uE3
Free bHCG
Pattern of PAPP-A and beta HCG increasing gestation (weeks 9-13 of pregnancy)
↑PAPP-A
↓hCG
Pattern of bHCG and PAPP-A with increasing risk in first trimester screening
↓PAPP-A
↑hCG
Normal trend of second trimester screening analytes with increasing gestation
↑AFP
↑uE3
↓free beta hCG
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