Adrenocorticotrophic hormone (ACTH)
ACTH stimulates secretion of Cortisol and androgens. Hypersecretion from a pituitary adenoma or hyperplasia causes cushing's disease (bilateral adrenal hyperplasia) which presents with the characteristic features of cushing's syndrome.
This syndrome may also be caused by excessive oral corticosteroids, but also by an adrenal tumour or by ectopic secretion from a bronchial carcinoma.
Features of Cushing's syndrome
- Moon face
- Hirsutism and baldness
- Buffalo-type obesity
- Purple striae over flanks and abdomen
- Muscle weakness and wasting
- Increased susceptibility to infection
- Latent diabetes mellitus
The diagnosis of a pituitary cause is suggested by finding normal or moderately raised ACTH levels which suppress with high doses of dexamethasone.
Ectopic ACTH production does not suppress with dexamethasone and with adrenal tumours, ACTH levels are virtually undetectable. Other tests include
- the effect of corticotrophin releasing factor (f ACTH if pituitary origin)
- petrosal versus peripheral venous sampling to identity the source of the ACTH.
Bilateral adrenalectomy for Cushing's syndrome is sometimes followed by the development of Nelson's syndrome - high ACTH levels, pituitary enlargement and marked skin pigmentation.
TSH - stimulates thyroid hormone secretion 1 Hypersecreting
FSH - controls growth of ovarian follicles/spermatogenesis > tumours LH - induces ovulation/testosterone secretion J very rare.
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