HPA

Question 1

What is the HPA axis?

Answer 1

Hypothalamic hormones stimulate the release of hormones from the anterior pituitary, which then act on the adrenal glands, thyroid, and gonads, among other targets. These target glands release their own hormones, which provide feedback to the hypothalamus and pituitary to regulate hormone levels.

Question 2

What is HPA axis suppression?

Answer 2

prolonged use of exogenous corticosteroids can suppress the HPA axis as high levels provide a negative feedback to the hypothalamus and pituitary, inhibiting the release of CRH and ACTH. This results in decreased stimulation of the adrenal glands and reduced endogenous cortisol production. Abrupt cessation of these medications can cause withdrawal symptoms due to the body’s reduced ability to produce cortisol and hence should be tapered gradually.

Question 3

What’s the Use of Tetracosactrin?

Answer 3

Adrenal gland secretion of cortisol is controlled by ACTH from the anterior pituitary.
Short Synacthen® (tetracosactrin) Test: used to investigate adrenal insufficiency.
Test evaluates the ability of the adrenal cortex to produce cortisol after stimulation by synthetic ACTH, i.e. assesses the ability of the adrenal gland to respond to ACTH; not reliable within two weeks of pituitary surgery.

Question 4

What happens in Glucocorticoid (cortisol) deficiency and what are the treatments?

Answer 4

decrease ACTH = decrease cortisol (adrenal insufficiency due to HPA axis dysfunction)
Treatment: hydrocortisone, prednisolone

Question 5

What happens in TH deficiency and what are the treatments?

Answer 5

low levels of TSH due to dysfunction of HPT axis which leads to insufficient stimulation of TH.
Treatment: T4 (thyroxine) replacement - requires tft monitoring
T3 replacement but less common.

Question 6

What happens in ADH deficiency and what are the treatments?

Answer 6

insufficient ADH = inability to concentrate urine (dilute urine) leading to excessive thirst and urination = diabetes insipidus.
Treatment: ADH agonist (desmopressin) - also has other uses such as decrease bleeding (ornipressin and terlipressin)

Question 7

What happens in pituitary tumours/ adrenomas?

Answer 7

non-cancerous tumours in the pituitary glands
symptoms: changes in vision, headache, hormonal imbalances

Question 8

What happens in hypogonadism and what are the treatments?

Answer 8

decrease in gonads (testes or ovaries)
hence replace with testosterone or oestrogen/ progestin

Question 9

What happens in growth hormone deficiency?

Answer 9

decrease in GH.
treatment: somatropin (recombinant human GH)

Question 10

What is acromegaly and what are the treatments?

Answer 10

excessive GH = increase insulin-like growth factor 1 (IGF1) = enlarged extremities such as ear, nose, jaws, hands and feet.
Can also increase sweating, lower glucose tolerance, etc.
Treatment aims to decrease IGF1 to normal range (SC Lanreotide, IM Octreotide)
- dopamine agonists: cabergoline, bromocriptine (dopamine inhibits GH secretion)
- Pegvisomant: GH receptor antagonist.

Question 11

What is hyperprolactinaemia and what are the treatments?

Answer 11

abnormal high levels of prolactin the blood - leads to pathological gambling, hypersexualism and psychosis
Treatment: dopamine agonist therapy - cabergoline, bromocriptine, quinagolide