Endocrinology Flashcards
Hypopituitarism
Due to deficiency of hypothalamic releasing hormone or pituitary hormones.
1 or hormones affected.
GH and FSH/LH usually affected late. ACTH and TSH affected first.
Hyperprolactinaemia occurs early due to break in its inhibitory pathway where it inhibits prolactin (PRL) release.
ADH and oxytocin are not affected as these are posterior pituitary hormones…unless hypothalamus involved or post pituitary is squashed by tumour or something.
Particular pituitary syndromes:
1) Congenital GnRH deficiency - Kallman’s syndrome
2) Sheehan’s syndrome - Pituitary infarction occurs for some reason after severe PPH. Rare in developed places
3) Pituitary apoplexy - rapid pit. enlargement due to bleeding into it or infarction. Pituitary becomes hulk - severe headache and visual loss (due to angry hulk in brain)
Treatment - Steroids and thyroid hormones - we need these to live. REPLACE THEM - DUAH
Hydrocortisone to replace steroids
Levothyroxine to replace thyroid hormones
Ensure normal glucocorticoid before replacing the thyroid hormone as the thyroid hormone will increase metabolic demand and without sufficient steroid hormones to assist, an adrenal crisis will occur
Hyperprolactinaemia
Normally, PRL under tonic inhibition by dopamine (DA) which the hypothalamus makes.
Pregnancy, severe stress such as exams, and lactation all increase PRL physiologically.
Commonest cause of prolactinaemia is a PRL-secreting pituitary adenoma. This occurs as the pituitary dumps its suppressive dopamine partner so it can live a full life.
Hypothyroidism can also cause increased PRL as TRH also stimulates PRL release.
Drugs include metoclopramide.
If PRL >5000 mU/L - its a bloody prolactin secreting tumour.
Men usually present later as their boobs need to work harder to make milk…so by the time they do their tumour has gotten pretty big.
The person presents with galactorrhoea. Headache and visual field defects if its a pituitary tumour causing it (most likely).
PRL also inhibits GnRH although no-one really knows why. This causes oligo/amenorrhoea and decreased libido, or a floppy one if you’re a guy.
Ix - Check serum PRL. At least 3 measurements.
TFTs to make sure it isnt hypothyroidism
Pituitary MRI to find the ntumour
Pituitary function and visual fields.
Treatment - Get rid of causative drugs
DA agonist - cabergoline (bromocriptine if preggers)
Observe if its just a microadenoma - give DA agnost though!
Transsphenoidal surgical resection is ideal.
What is an endocrine hormone?
Hormone produced by ductless glands released directly into the blood
What is an autocrine hormone?
A hormone that acts on the cell that itself secreted it
What is a paracrine hormone?
A hormone that acts on cells neighboring the cells that secrete it
What is an endocrine hormone?
A hormone that acts on distant sites, carried by the blood
What is a phermonal hoormone?
A hormone released into the atmosphere
Where are oyxytocin and ADH produced and then stored?
Produced in hypothalamus then stored in posterior pituitary gland
What does the pineal gland do?
Melatonin: control of body rhythms
Where does the pituitary gland sit
Near the optic chiasm in the sella turcica
What does corticotrophin (ACTH) do?
Stimulates release of adrenal cortex hormones
What does growth hormone do?
Acts on most of our cells - promoted skeletal and muscle growth
What does LH do?
ruptures ripe Graafian follicle.
Releases ovarian oestrogens and testicular testosterone
What does FSH do?
Promotes follicular growth, and spermatogenesis
What actions does oxytocin have?
Stimulates milk release and uterine contractions
