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RACP > Endocrinology > Flashcards

Endocrinology Flashcards

1
Q

MEN syndromes

A

Men 1 - Pituatory adenoma, parathyroid hyperplasia, pancreatic tumours - P’s!

Men 2a - Parathyroid hyperplasia, Medullary thyroid malignancies, pheochromocytoma - associated with RET gene gain of function mutation (loss of function Hirshsprung)

Men 2b - Mucosal neuromas, Marfans, Parathyroid Hyperplasia, Pheochromocytoma

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2
Q

PCOS diagnosis

A
  • Androgen Excess
  • Oligomenorrhoea
  • > 12 cysts per ovary of > 2mm, with one ovary > 10ml

Hormones
- High LH
- High Testosterone
- High/Normal oestrogen
- High LH:FSH ratio

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3
Q

MODY

A

Mature onset Diabetes of the young

Monogenic diabetes; result from mutations or changes in a single gene; presents with strong family history of diabetes

  • MODY 1 - least common, due to HFN4
  • MODY 2 - GCK mutation, results in mildly high fasting glucose without complications. Only require treatment in pregnancy
  • MODY 3 - HFNA1 mutation, most common, sensitive to sulphonylureas
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4
Q

Vitamin D pathway

A

7-dehydrocholesterol -> Vitamin D3 (cholecalciferol) via UV -> 25-hydroxyvitamin D3 in liver -> 1, 25 hydroxyvitamin D3 (calcitriol) via 1-alpha hydroxylase at kidney.

1-alpha hydroxylase in kidney is inhabited by FGF-23 during Klotho deficiency in CKD

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5
Q

Familial Hypocalcuric hypercalcaemia

A

Calcium receptor in parathyroid gland requires higher levels of calcium to down regulate PTH
PTH levels will be normal at high calcium levels
PTH will continue to reabsorb calcium from kidneys

  • High Calcium
  • Normal PTH
  • Low urinary calcium
  • Urine Ca:CR ratio calculated with Hammersmith equation
  • Surgery contraindicated
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6
Q

Addison’s disease

A
  • Primary adrenal insufficiency
  • Congenital; 21 hydroxylase deficiency
  • Autoimmune; 21-hydroxylase antibodies
  • High ACTH with tanned skin
  • No response with short synacthen
  • Low cortisol
  • Hypoaldosteronism, high K+, low Na+
  • High Renin
  • Loss of sex characteristics
  • Associated with autoimmune polyglandular syndrome
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7
Q

Deiodinase inhibitors

A

Amiodarone, Steroids, Propanolol
Block conversion of T4 to T3

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8
Q

Turners syndrome

A

XO genotype
Primary ammenorhoea & poor breast development
Short stature
Bicupsid aortic valve - requires surveillance
Autoimmune thyroiditis
Auditory dysfunction
Metabolic syndrome
Horseshoe kidney

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9
Q

Acromegaly investigations

A

IGF-1 level (has long half life and decreased variation in comparison to GH)
High growth hormone & IGF-1 during Glucose Tolerance test
Pituitary MRI

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10
Q

PTH action at kidney, bone & gut

A

Kidney * PTH = Phosphaturia*
- Decreased calcium excretion
- Increased phosphate excretion
- Increase 1-alpha-hydroxylase activity

Gut
- Increased calcium and phosphate resorption

Bone
- Remodelling by binding PTH receptors at osteoblasts (osteoclasts lack PTH receptors)
- Upregulates RANK ligand which in turn stimulates osteoclasts (indirect activation of osteoclasts)

But if pulsatile exposure to PTH i.e with Teriparatide this will increase osteoblasts and help with osteoporosis!

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11
Q

PTH - Calcium curve shifts

A

Familial Hypocalcuric hypercalcaemia - shifts RIGHT
Autosomal dominant hypocalcaemia - shifts LEFT
Cinacalcet- shifts curve to left

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12
Q

Indications for surgery in primary hyperparathyroidism

A

Serum calcium > 2.80
BMD T score < 2.5 or fragility fracture (strongest indication!)
Age < 50
eGFR < 60
24 hour urinary calcium > 10mmol

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13
Q

FGF-23

A

Secreted by Osteoclasts

Driven by ‘Klotho deficiency’

Causes phosphate wasting by 2 mechanisms;
- Inhibits 1-alpha-hydroxylase to decrease formation of 1,25-hydroxyvitamin D & downregulates PO4 absorption at GIT
- Induces phosphate excretion in kidneys via NPT2a sodium-potassium cotransporter

  • High FGF-23 leads to hypophosphataemia and rickets
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14
Q

Whipples Triad

A
  • Hypoglycaemia below 3.1
  • Neuroglycopenic symptoms
  • Resolution of symptoms with glucose ingestion
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15
Q

Thiazolidinediones

A

Sensitise insulin via PPAR activation which makes cells more dependent on glucose with increased peripheral uptake

Increased risk of CVD, bladder malignancy and fractures

i.e. Rosiglitazone

Note: fenofibrate are also PPAR activators

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16
Q

Production testosterone in males

A

GnRH pulsing -> LH -> Leydig cells -> testosterone
- testosterone -> oestradiol via Aromatase
- testosterone -> dihydrotestosterone via 5-alpha reductase
- testosterone acts at Sertoli cells with FSH to induce spermatogenesis

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17
Q

Decreased SHBG

A
  • Hypothyroidism
  • Glucocorticoids
  • Nephrotic syndrome
  • Growth hormone excess
  • Obesity
  • Insulin resistance

Associated with increased free testosterone

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18
Q

Liver derangement with Graves Rx

A
  • Carbimazole = cholestatic
  • PTU = hePaTocellUlar
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19
Q

Adiponectin

A

Released by adipose tissue in states of decreased body fat (levels inversely related to body fat)

Will be LOW in obesity
- decreasing catabolism of fats and increasing insulin resistance
- Low adiponectin levels predict diabetes in Pima Indians

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20
Q

Physiology of appetite

A

Orexegenic - Ghrelin acting at Neuropeptide Y neutron in hypothalamus to release Agouti-related peptid and Orexin. Agouti-related peptide competitively binds MC4 receptors to increase hunger

Anorexigenic - Leptin binds to POMC neurons at the hypothalamus to release Alpha-MSH which competitively binds to MC4 receptors to decrease hunger, along with inhibiting Agouti-related peptide release (Leptin = Less)

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21
Q

Hormones that stimulate appetite

A

Easier to remember the hormones that stimulate appetite (only 3);
- Ghrelin
- Neuropeptide Y
- Agouti-related peptide

The rest inhibit appetite!

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22
Q

Actions of GLP1 agonists

A
  • Increases beta cell number and therefore production of insulin via GLU2
  • Inhibits production of glucagon
  • Suppresses appetite
  • Slows gastric emptying

GLP-1 is usually inhibited by DPP-4 (which is why DPP-4 inhibitors work i.e. Linagliptin)

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23
Q

Congenital adrenal hyperplasia

A

Due to 21-hydroxylase deficiency which prevents aldosterone and cortisol production -> shunts 17-hydroxyprogesterone to testosterone

Common in patients with bilateral adrenal lesions
Can cause ambiguous genitalia in females

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24
Q

Layers of adrenal gland

A

Adrenal Cortex (GFR)
Zona glomerulosa- aldosterone
Zona fasciculata- cortisol
Zona reticularis- DHEA, Androstenedione

Adrenal Medulla
Adrenaline
Noradrenaline
Dopamine

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25
Q

Indications for Inferior petrosal sinus sampling

A

Confirmatory test for ACTH dependent cushings where pituitary adenoma is < 6mm.
- If ACTH central:peripheral > 2:1 then for pituitary surgery
- If ACTH central:peripheral < 2:1 then consider ectopic ACTH production i.e. lung cancer

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26
Q

Jon Basedow Effect

A

Ingestion of Iodine causes Hyperthyroidism in glands that are not under pituitary control i.e. Graves, TMG, Endemic goitres

Effect seen in Type 1 amiodarone induced thyroiditis where iodine overload causes hyperthyroid in abnormal glands

27
Q

Wolff Chaikoff effect

A

Ingestion of Iodine load causes hypothyroidism as a means of autoregulation

Normal thyroid glands will overcome this - “escape”, but those with autoimmune thyroiditis will not overcome this hypothyroidism (fail to escape phenomenon)

28
Q

Type 1 Amiodarone induced thyroiditis

A
  • Occurs within weeks of ingestion
  • Hyperthyroidism due to iodine load
  • Occurs in abnormal glands (Jod Basedow effect)
  • Increased vascularity on USS
  • Treated with Carbimazole
29
Q

Type 2 Amiodarone induced thyrotoxicosis

A
  • Occurs within years of ingestion
  • Destructive thyroiditis causing release of pre-formed thyroid hormone
  • Occurs in normal glands
  • Normal vascularity on USS
  • Raised thyroglobulin and IL6
  • Treat with steroids
30
Q

Features of Thyroid malignancy on USS

A

Irregular margins
Cervical lymphadenopathy
Absence of Halo sign
Hypoechogenicity
Solid lesion
Intranodular vascularity
Taller than wide
> 1cm

Determine TiRAD score

31
Q

Indication for FNA in thyroid nodule

A

TIRADS 1-2 No FNA
TIRADS 3 > 2.5cm
TIRADS 4-6 > 1.5cm
TIRADS 7 > 1cm

If FNA positive;
Total thyroidectomy is required for all primary tumour of >1cm or if extranodal extension or metastases present

Any nodule > 4cm requires lobectomy regardless of features or biopsy result

32
Q

Types of thyroid malignancy

A

Papillary - 80%, young females, Familial adenomatous polyposis Hx, monitor thyroglobulin
Follicular - 10% , monitor thyroglobulin
Medullary - cancer of parafollicular cells, associated with MEN2a, secrete calcitonin. Poor prognosis with mets.
Anaplastic - non-responsive to treatment and aggressive. Very poor prognosis.

33
Q

Sick Euthyroid

A

Inhibition of deiodinase and therefore conversion T4 to T3
- Reduces T3
- Increases reverse T3 (unclear clinical significance)
- Normal T4 and TSH
- T4 and TSH can decrease in severe illness
In recovery, TSH transiently rises to 10 - if TSH rebound > 10, likely patient has underlying hypothyroidism

34
Q

Management of thyroid malignancy

A

TIRADS score
- FNA if > 1cm and suspicious
- Lobectomy for any lesion > 4cm, even if FNA negative

  1. Thryoidectomy
    - Any lesion > 4cm
    - Malignant lesion > 1cm
  2. Post-op radio iodine therapy - to help with monitoring of reoccurance
  3. TSH suppression with thyroxine (aim to suppressive TSH with thyroxine doses above physiological levels)
  4. Monitor Thyroglobulin or Calcitonin
    If suppressing TSH with Thyroxine - may need to give recombinant human TSH to stimulate thyroglobulin and monitor levels
35
Q

High T3, T4 and TSH

A

TSH secreting pituitary adenoma

36
Q

MOA Carbimazole

A

Prodrug converted to Methimazole

Inhibits iodination of thyroglobulin by blocking thyroid peroxidase

Side effects
- Agranulocytosis
- CholestatiC picture (PTU = HePaTic)
- Teratogenic; scalp defects
- GI upset
- Rash

37
Q

Teriparatide

A

Binds PTH receptor
- PTH will act anabolically at intermitted dosing
- Only anabolic agent for the treatment of severe osteoporosis, (rest are anti-remodelling agents)

Used for treatment not prevention

38
Q

Thiazide diuretic and calcium

A

Block sodium-chloride co-transporter resorption & subsequently up regulates sodium-calcium transporter leading to hypercalcaemia

  • hypercalcaemia
  • hypokalaemia
39
Q

Reason for Hyponatraemia in primary adrenal insufficiency

A
  • Increased CRH which stimulates ADH
  • Hypoaldosterone
40
Q

Amiodarone effects on Thyroid

A
  • Decreases conversion T4 to T3, with decreased negative feedback on TSH resulting in high TSH and T4 with low T3
    -Wolff Chaikoff effect; Ingestion causes Hypothyroidism due to autregulatory negative feedback
  • T1 AT - Jon Basedow effect; increased iodine causes hyperthyroidism
  • T2 AT - Release of stored T3 and T4 due to inflammation
41
Q

Thyroid hormone changes in pregnancy

A
  • Decreased TSH with rising HcG in first trimester (inverse relationship)
  • Increased thyroxine binding globulin & mobilisation of T3 and T4 (stimulated by high oestrogen state and decreased hepatic clearance)
  • Increased Iodine requirements (and potential for goitre if not adequate)
  • Ensure measurement of TRAB in pregnant patients with graves to stratify risk of neonatal hyperthyroidism
  • Treat hyperthyroidism with PTU in first trimester (hepatotoxicity), then Carbimazole in second and third (scalp defects)
42
Q

Indications for treatment of subclinical hypothyroidism

A
  • Pregnancy
  • TSH level > 10
43
Q

Kallmans syndrome

A

Dominant X-linked disorder
Lack of GnRH causing inadequate LH and FSH -> Low testosterone and oestrogen
- Small testes or small breasts
- Primary amenorrhoea in females
- Anosmia due to aplasia of olfactory bulb
- In men and women who desire fertility, replacement of LH and FSH is necessary as alternative as exogenous testosterone and oestrogen suppresses spermatogenous and ovulation
- Can have mild cognitive impairment

44
Q

BSL targets in pregnancy

A

Fasting and pre-prandial 4.0–5.5mmol/L
Post-prandial less than 8.0mmol/L at 1h or less than 7mmol/L at 2h

45
Q

Mechanism SGLT2 inhibitors

A

Block SGLT2 on the apical membrane of proximal tubule cells to decrease glucose resorption

  • Reduces HbA1c%
  • Mild reduction BP
  • Reduces CVS events
  • Mild weight loss
  • Reduced uric acid
  • Reduced microalbuminuria
46
Q

SGLT2 side effects

A
  • Euglycaemic ketoacidosis
  • UTI
  • Increased risk amputations
  • Increased risk atypical fractures
  • Dehydration
47
Q

Investigations for Cushings Syndrome

A
  1. 24 hour urinary cortisol
  2. ACTH (+/- dexmethasone high or low dose - but not recommended anymore!)
  3. Imaging
48
Q

Vitamin D synthesis

A

-7-dehydrocholesterol to cholecalciferol (Vitamin D3) via UV light, or Vitamin D3 directly from diet

-Cholecalciferol to calcidiol (25 hydroxyvitamin D) in liver

-Calcidiol to calcitriol in kidneys (1.25 hydroxyvitamin D) via 1 alpha-hydroxylate

49
Q

Bound testosterone and Oestrogen

A

60% bound to SHBG
40% bound to Albumin
< 2% free

50
Q

Changes in SHBG

A

Increased SHBG - less free androgens

Ageing
Hyperthyroidism
Liver disease
HIV
Oestrogen
Phenytoin
Tamoxifen

Decreased SHBG - more free androgens

Obesity -> weight loss improves PCOS
Insulin resistance
Hypothyroidsim
GH excess
Steroids
Androgens or progestins
Nephrotic syndrome

51
Q

NAGMA

A

ABCD
•Addisons (adrenal insufficiency)
•Bicarbonate loss (GI or Renal)
•Chloride excess
•Diuretics (Acetazolamide)

52
Q

Post-exercise hypoglycaemia in diabetics

A
  • Decrease long-acting insulin
  • Consume carbs pre-bed post-exercise
  • Ensure BSL > 7 pre-bed
53
Q

Diagnosis and Rx Acromegaly

A

inadequate suppression GH and IGF-1 with GTT
Rx Octreotide (somatostatin analogue), Pegvisomant (GH receptor antagonist) or Cabergoline

Somatostatin has negative feedback on GH release

54
Q

Cinacalcet MOA

A

Calcium mimetic to negatively feedback on PTH

55
Q

Drugs inducing hyperprolactin

A
  • Antipsychotics ie. respiradone
  • Anti-emetics - Metaclopramide/Domperidone
  • Antidepressants - TCAs, MAOi’s
  • Analgesia - Opioids
  • Anti-hypertensives - Verapamil, Methyldopa
56
Q

Genetic factors of obesity

A

Low adiponectin
MC4-r mutations

56
Q

Leptin and Ghrelin

A

Leptin reduces appetite by releasing MSH- alpha from POMC to act at MC4-receptors. Also inhibits Ghrelin release.

Ghrelin increases appetite by releasing Agouti-related peptide via Neuropeptide Y to act on MC4-R receptors. Increased levels in Prader WIlli syndrome.

56
Q

Congenital Adrenal Hyperplasia

A
  • Due to 21 hydroxylase deficiency
  • Shunts to form testosterone instead of aldosterone and cortisol
  • High levels of hydroxyprogesterone
  • Often results in bilateral adrenal lesions
  • Most common cause of ambigous genitalia
  • Low cortisol
  • Low aldosterone
  • High Testosterone
57
Q

Hormone changes pregnancy

A

Increased beta-HCG

Increased T3 & 4, but Increased Thyroid binding globulin with decreased free T3/4

Decreased TSH in first trimester but will start to increase with B-HcG decline

Increased oestrogen and testosterone

Decreased LH & FSH

Increased prolactin

58
Q

Secondary hyperaldosteronism

A
  • High Renin
    Ddx;
  • Renal Artery stenosis
  • Aortic coarctation
  • Reninoma
  • Gitelmans syndrome - mimics thiazide in grown-ups
  • Barters syndrome - mimics loop diuretics in Babies
59
Q

Primary hyperaldosteronism

A
  • Aldosterone secreting Adenoma (Conns syndrome)
60
Q

Acarbose MOA

A

Glucosidase inhibitor to reduce saccharine breakdown & resorption at GI tract

61
Q

MUDPILES

A

Causes of anion gap metabolic acidosis
MUDPILES
Methanol
Uraemia
DKA
Paracetamol overdose
Isoniazid
Lactic acidosis
EtOH
Salicylates

62
Q

Causes NAGMA

A

USED CAR
- Utero-enterostomy
- Small bowel fistula, pancreatic fistula
- Extra Chloride
- Diarrhoa
- Carboic anhydrase inhibitors (Acetazolamide - prevents resorption HCO3)
- Addisons disease
- RTA

RACP (17 decks)

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