Pituitary

Question 1

Name the 5 hypothalamic hormones which act on the pituitary gland

Answer 1

Growth hormone releasing hormone (GHRH), gonadotrophin releasing hormone (GnRH), thyrotrophin releasing hormone (TRH), dopamine, corticotrophin releasing hormone (CRH)

Question 2

Name the two hormones released by TRH acting on the pituitary

Answer 2

Thyroid stimulating hormone (TSH), prolactin

Question 3

State three contraindications to the combined pituitary function test

Answer 3

Ischaemic heart disease, epilepsy, untreated hypothyroidism

Question 4

Describe the side effects of the combined pituitary function test

Answer 4

SEs of hypoglycaemia: sweating, palpitations; rarely, loss of consciousness, convulsions
SEs of TRH injection: metallic taste in the mouth, flushing, nausea

Question 5

Which three substances are given in a combined pituitary function test?

Answer 5

GnRH, TRH, insulin

Question 6

At which points during the combined pituitary function test are pituitary hormone levels measured?

Answer 6

0, 30, 60, 90, and 120 minutes

Question 7

What is an adequate cortisol response to an insulin tolerance test?

Answer 7

Increase greater than 170nmol/l to >500nmol/l

Question 8

What is an adequate GH response to an insulin tolerance test?

Answer 8

Increase greater than 6mcg/l

Question 9

What is a normal response to a thyrotrophin releasing hormone test?

Answer 9

TSH rise to >5mU/l, with 30min value greater than 60min value

Question 10

What are the responses to a thyrotrophin releasing hormone test in hyperthyroidism and hypothyroidism?

Answer 10

Hyperthyroidism: TSH remains suppressed
Hypothyroidism: exaggerated response

Question 11

What is a normal response to a gonadotrophin releasing hormone test?

Answer 11

Peak at 30 or 60 mins with LH >10U/l and FSH >2U/l

Question 12

How is gonadotrophin deficiency diagnosed in males?

Answer 12

Low testosterone in the absence of raised basal gonadotrophins

Question 13

How is gonadotrophin deficiency diagnosed in females?

Answer 13

Low oestradiol in the absence if elevated basal gonadotrophins and with no response to clomiphene

Question 14

What are the cutoff sizes for pituitary micro and macro-adenomas?

Answer 14

Microadenoma: <10mm
Macroadenoma: >10mm

Question 15

What is the main sign of a pituitary adenoma?

Answer 15

Bitemporal hemianopia

Question 16

Name the two anterior pituitary hormones

Answer 16

Anti-diuretic hormone (ADH, vasopressin), oxytocin

Question 17

State the three main causes of excess ADH

Answer 17

Lung paraneoplasias (small cell lung cancer), CNS pathology, iatrogenic

Question 18

State at least three iatrogenic causes of excess ADH

Answer 18

SSRIs, amitryptiline, carbamazepine, proton-pump inhibitors (PPIs)

Question 19

What is the consequence of excess ADH?

Answer 19

SIADH, causing euvolaemic hyponatraemia

Question 20

What is diabetes insipidus?

Answer 20

Increased diuresis due to either failure of production of ADH or loss of sensitivity to ADH, leading to decreased urine osmolality and increased serum osmolality

Question 21

State three causes of nephrogenic diabetes insipidus

Answer 21

Lithium, hypercalcaemia, renal failure

Question 22

What is dipsogenic ADH failure?

Answer 22

Damage to the hypothalamus and thirst drive causing hypernatraemia without an increased thirst response