Endocrinology

Question 1

Where is the site of action of antidiuretic hormone (ADH)?

Answer 1

Collecting ducts: stimulates water reabsorption by inducing expression of aquaporin 2 channels

Question 2

How can lithium use cause nephrogenic diabetes insipidus?

Answer 2

The kidneys cannot respond adequately to antidiuretic hormone (ADH) as lithium inhibits the expression of aquaporin-2 channels in the renal collecting duct rather than the distal convoluted tubule

Question 3

When does central diabetes insipidus occur?

Answer 3

Damage to the posterior pituitary gland: insufficient production and release of ADH

Question 4

Addison’s disease signs and symptoms

Answer 4

result of low aldosterone & low cortisol:

• lethargy, weakness, anorexia, nausea & vomiting, weight loss, ‘salt-craving’
• hyperpigmentation (especially palmar creases), vitiligo, loss of pubic hair in women, hypotension, hypoglycaemia
• hyponatraemia and hyperkalaemia
• crisis: collapse, shock, pyrexia

Question 5

Most common cause of adrenal insufficiency

Answer 5

Addison’s disease (primary adrenal insufficiency) = autoimmune destruction of the adrenal glands
- often seen with other autoimmune diseases such as diabetes type 1

Question 6

Congenital adrenal hyperplasia

Answer 6

Enzyme deficiency e.g. 21 hydroxylase deficiency = Low production of cortisol = Compensatory hyperplasia

Most commonly due to 21-hydroxylase deficiency

Features:
virilisation (making more masculine) of female genitalia
60-70% of patients have a salt-losing crisis at 1-3 wks of age

Question 7

Tertiary Hyperparathyroidism

Answer 7

High Ca2+, Inappropriately elevated PTH, Low Phosphate

Ongoing hyperplasia of the parathyroid glands after correction of underlying renal disorder, hyperplasia of all 4 glands is usually the cause

Question 8

Primary Hyperparathyroidism

Answer 8

Elevated Ca2+, Elevated PTH, Low Phosphate

Most cases due to solitary adenoma (80%)

Question 9

Secondary Hyperparathyroidism

Answer 9

Low Ca2+, Appropriately elevated PTH, Elevated Phosphate

Parathyroid gland hyperplasia occurs as a result of low calcium, almost always in a setting of chronic renal failure

Question 10

Example of a steroid with very high glucocorticoid activity and minimal mineralocorticoid activity

Answer 10

Dexamethasone

Question 11

What does the adrenal medulla secrete?

Answer 11

Catecholamines (adrenaline and noradrenaline)

Test for phaeochromocytoma: urinary free adrenaline

Question 12

Where is cortisol produced?

Answer 12

The zona fasciculata of the adrenal cortex
Test for Cushing’s disease (high cortisol): 24-hour urinary free cortisol
Test for Addison’s disease (low cortisol): short synacthen test (ACTH injection then measure cortisol)

Question 13

Where is aldosterone produced?

Answer 13

Zona glomerulosa of the adrenal cortex

Test for Conn’s disease: aldosterone-renin ratio

Question 14

Where are androgens produced?

Answer 14

Zona reticularis of the adrenal cortex

Question 15

Where are glucocorticoids produced?

Answer 15

Zona fasciculata of the adrenal cortex

Question 16

Example of a steroid with minimal glucocorticoid activity and very high mineralocorticoid activity

Answer 16

Fludrocortisone

Side effects of mineralocorticoid activity: fluid retention,

Question 17

What do mineralocorticoid steroids mimic?

Answer 17

Aldosterone = regulation of sodium and water retention in response to low blood pressure.

Question 18

What do glucocorticoid steroids mimic?

Answer 18

Cortisol = carbohydrate metabolism and the stress response.

Question 19

Side effect of steroids with high mineralocorticoid activity?

Answer 19

Fluid retention, hypertension

Question 20

Side effect of steroids with high glucocorticoid activity?

Answer 20

Depression, hyperglycaemia, osteoporosis and peptic ulceration
= need to do four times daily capillary blood glucose in patients with diabetes on high glucocorticoid steroids

Question 21

Features of Addisonian/Adrenal crisis

Answer 21

Fatigue, syncope, hyperpigmentation, hypotension, hypoglycaemia, hyponatraemia and very low cortisol.

Question 22

Which cells release renin

Answer 22

Juxtaglomerular cells

Question 23

Which cells produce ACE

Answer 23

Pulmonary endothelium

Question 24

Lipodystrophy

Answer 24

Insulin can cause small subcutaneous lumps at injection sites (can be prevented by rotating the injection site)

Question 25

HCG secreting seminoma

Answer 25

Type of seminoma and a germ cell tumour. Human chorionic gonadotropin (HCG) = this hormone can cause oestrogen production out of proportion with normal androgens, resulting in gynaecomastia in males

Question 26

Octreotide

Answer 26

Prescribed for Acromegaly: Somatostatin analogue | = Somatostatin directly inhibits the release of growth hormone

Question 27

Hypospadias

Answer 27

Birth defect in boys in which the opening of the urethra is not located at the tip of the penis Cryptorchidism (undescended testes) is present in around 10% of patients with hypospadias

Question 28

Thiazolidinediones (e.g. pioglitazone)

Answer 28

Activate the peroxisome proliferator-activated receptor gamma (PPAR gamma) and modulate the transcription of genes involved in glucose and lipid metabolism = overall increases insulin sensitivity and decreases hepatic glucose production !! contraindicated in patients with heart failure.

Question 29

Sulphonylureas (e.g. gliclazide)

Answer 29

Bind to KATP channels on pancreatic beta cells to stimulate insulin release ! weight gain ! hypoglycaemia risk

Question 30

Sodium-glucose co-transporter-2 (SGLT2) inhibitors

Answer 30

(also known as the 'flozins') Inhibit renal glucose reabsorption = promote glycosuria !! increase the frequency of urinary tract infections

Question 31

Dipeptidyl peptidase-4 (DPP-4) inhibitors

Answer 31

(also known as the 'gliptins') Inhibit the breakdown of incretins by the DPP-4 enzyme. = the increased circulating incretins (such as GLP-1 and gastric inhibitory polypeptide) promote glucose-dependent insulin release from the pancreas Weight-neutral

Question 32

Posterior pituitary hormones

Answer 32

Oxytocin and ADH

Question 33

Tanner stages

Answer 33

Development before puberty scale | 5 stages

Question 34

Characteristic histology finding in papillary thyroid cancer

Answer 34

Orphan Annie eyes with psammoma bodies

Question 35

What is the commonest bacterial cause of Waterhouse-Friderichsen syndrome (adrenal haemorrhage)?

Answer 35

Neisseria meningitidis

Question 36

Three unique signs of Graves disease

Answer 36

thyroid eye disease, thyroid acropachy, and pretibial myxoedema

Question 37

Test to diagnose diabetes insipidus

Answer 37

Water deprivation test

Question 38

Features of Multiple endocrine neoplasia (MEN) type IIb

Answer 38

Medullary thyroid cancer, phaeochromocytoma, marfanoid body habitus

Question 39

Magnesium levels must be checked in a hypoparathyroid biochemistry

Answer 39

Magnesium allows parathyroid hormone to exert its effects: magnesium enables secretion and function of parathyroid hormone.

Question 40

What is the first hormone to be secreted in response to hypoglycaemia?

Answer 40

Glucagon

Question 41

What antibodies are present in 90% of Hashimoto's thyroiditis cases?

Answer 41

Anti-thyroid peroxidase (anti-TPO) antibodies

Question 42

Why does primary hyperparathyroidism cause hypophosphataemia?

Answer 42

Parathyroid hormone causes a decrease in renal phosphate reabsorption - excessive levels of PTH, as found in hyperparathyroidism, can lead to low serum phosphate levels due to reduced renal reabsorption.

Question 43

Why can risperidone cause galactorrhoea?

Answer 43

Risperidone is an atypical antipsychotic. All antipsychotics have the potential to raise prolactin. This is because they inhibit dopamine, subsequently reducing dopamine-mediated inhibition of prolactin.

Question 44

Why does treatment of DKA present with hypokalaemia?

Answer 44

Treatment = Insulin: decreases serum potassium through stimulation of the Na+/K+ ATPase pump

Question 45

What is the half life of insulin in the circulation of a normal healthy adult?

Answer 45

>30 minutes

Question 46

Water deprivation test in primary polydipsia

Answer 46

urine osmolality after fluid deprivation: high | urine osmolality after desmopressin: high

Question 47

Which is the primary ketone body involved in diabetic ketoacidosis?

Answer 47

acetoacetate (as well as b-hydroxybutyrate) | breakdown product = acetone

Question 48

Ketone bodies

Answer 48

Produced by the liver from fatty acids. Produced during periods of fasting/starvation, intense exercise, or in untreated type 1 diabetes mellitus. They are picked up by the extra-hepatic tissues, and converted into acetyl-CoA which then enters the citric acid cycle and is oxidized in the mitochondria for energy.

Question 49

Why does alcohol cause a late hypoglycaemia?

Answer 49

Carbohydrates in alcoholic drinks can cause blood glucose to rise. This is then followed by the alcohol inhibiting glycogenolysis = late hypoglycaemia.

Question 50

Hypoglycaemia (plasma glucose level of less than 4.0 mmol/L) treatment

Answer 50

If the patient is conscious and able to swallow the first-line treatment is a fast-acting carbohydrate by mouth i.e.. glucose liquids, tablets or gels If the patient is unconscious or unable to swallow, subcutaneous or intramuscular injection glucagon may be given. Alternatively, intravenous 20% glucose solution may be given through a large vein

Question 51

How does Cushing's affect potassium concentration?

Answer 51

Results in hypokalaemia In high concentrations cortisol can exhibit mineralocorticoid (e.g. aldosterone) activity by binding to and activating Na+/K+ pumps. This causes the movement of potassium into the cells and can result in hypokalaemia.