Hypothalamus + pituitary Flashcards
What is the embryonic origin of the anterior pituitary?
Arises from the ectoderm that grows from the roof of the mouth (RATHKE’S POUCH)
What is the embryonic origin of the posterior pituitary?
Arises from the diencephalon of the brain
Which of the pituitary hormones do somatostatin and dopamine inhibit?
Somatostatin: GH and TSH
Dopamine: Prolactin
What stimulates the pituitary hormone ACTH?
- CRH
- ADH
What stimulates the pituitary hormone FSH?
- kisspeptin
- GnRH
What stimulates the pituitary hormone GH?
- GHRH
- Ghrelin
What stimulates the pituitary hormone TSH?
- TRH
What stimulates the pituitary hormone PRL?
- TRH
Where is the defect in primary and secondary underactivity of thyroid hormone production?
Primary: defect in THYROID gland (e.g. Hashimoto’s)
Secondary: defect in PITUITARY (could be due to a tumour)
What does GH stimulate the production of?
IGF-1
What is the effect of IGF-1 production on pituitary hormones?
IGF-1 produces somatostatin and inhibits GH and GHRH
What is the role of GHRH?
- Promote GH cell clusters
- Increase GH cell number
- Increase GH synthesis
- Stimulate GH release
What is McCune-Albright syndrome?
- spontaneous (somatic) mutation in embryo
- prevents downregulation of cAMP (interferes with G-protein signalling)
- Results in:
1. hyperfunctioning endocrine organs (goitre)
2. bone deformities
3. skin discolouration (café au-lait spots) - more common in females than males
Describe the hypothalamo-pituitary-adrenal axis.
- corticotrophin releasing hormone and ADH in the hypothalamus stimulates the pituitary
- in response the pituitary releases ACTH which stimulates the zona fasciculata of the adrenal cortex
- cortisol production results in negative feedback to the hypothalamus and pituitary
Which syndromes are associated with a deficit and excess of cortisol?
Excess = Cushing's syndrome Deficit = Addison's disease
Explain the 2 different types of Cushing’s syndrome.
- ACTH independent: ACTH does not impact cortisol levels
- adrenal tumour can cause inappropriate cortisol release = increased cortisol downstream - ACTH dependent: ACTH levels increase (may be due to pituitary defect such as adenoma)
What are the symptoms of Cushing’s syndrome?
Symptoms:
- weight gain
- muscle weakness
- skin changes (dry, flaky skin)
Explain the gonadal axis.
- Kisspeptin stimulates GnRH
- GnRH stimulates LH and FSH
- LH and FSH are inhibited by inhibin
- production of LH and FSH = oestrogen and testosterone production in gonads
- positive feedback mechanism via oestrogen and negative feedback via testosterone
