Causes of raised and suppressed growth hormone
Suppressed by: hyperglycaemia, somatostatin, chronic corticosteroid use. Stimulated by hypoglycaemia, oestrogen, ghrelin
Diagnosis of acromegaly
- Raised IGF-1
- 75g OGTT fails to suppress GH
- MRI pituitary to localise
- Check prolactin (co-secreted in 25%), TFTs, FSH/LH
Most common cause of congenital adrenal hyperplasia
- 21-hydroxylase deficiency (CYP21A2) - impaired c onversion of 17-OH-progesterone to 11-deoxycortisol
- increased DHEA and testosterone, low cortisol -> h igh ACTH causes adrenal hyperplasia
- Female virilisation / ambiguous genitalia if prenatal, male precocious puberty
- Raised 17-OH progesterone baseline + post-synacthen
Biochemical profile of primary, secondary adrenal insufficiency
Early morning cortisol low if not on steroids; SST fails to stimulate cort (unless recent pit damage - haemorrhage, surgery); insulin tolerance test - normally cort > 550, GH >20
ACTH high (primary) or low
Renin high, aldo low (primary)
DHEAS low
What does gastrin do and where is it secreted from
Secreted from stomach Antrum G cells
Gastrin is the dominant mediator of poatprandial gastric acid production Increases - HCl, Intrinsic factor, pepsinogen - gastric mucosal growth & motility 🍣🍘🍦🍭🍫🍰🍢🍱🍵🍜🍤🧀🍝
What decreases the production of gastrin?
Somatostatin (Dcells) stomach
Secretin (S cells) Small intestine
They are both stimulated by low pH. They provide negative feedback
Secretin also stimulates HCO3- release from pancreas
What causes hypergastinemia?
- prolonged Acid inhibition (PPI, H2 antagonist)
- Atrophic gastritis (pernicious anemia, H.pylori)
- Gastrinoma
(Think MEN1) - Vagotomy, small bowel resection
Issues treating concurrent hypothyroidism with adrenal insufficiency (e.g. Autoimmune polyglandular syndrome)
Adrenal crisis can be precipitated by starting thyroxine due to accelerated metabolic clearance of cortisol
Treatment of adrenal insufficiency
Cortisone 37.5mg/d (25/12.5)
Or hydrocortisone 20mg/d (10/5/5)
Fludrocortisone 100-200mcg/d in primary only
