endocrinology Flashcards
Primary hormone for stimulating both synthesis and secretion of GH from somatotrophs?
Growth hormone releasing hormone (GHRH)
Primary physiologic effect of growth hormone?
stimulation of postnatal longitudinal growth
which family of receptors do growth hormone cell surface receptors belong to?
Class 1 cytokine receptors
primary physiologic role of prolactin
stimulation of milk production
what is the major stimulus for ADH release?
Osmoreceptors in the hypothalamus and in the lamina terminalis detect osmolarity of ECF
What is the vascular connection between hypothalamus and anterior pituitary?
hypophyseal portal system: concentrated neurohormones are secreted into capillary network and affect target organs. small amounts can have potent effect
what is the neural connection between hypothalamus and posterior pituitary?
hypothalamic nuclei (supra optic and paracentricular) project axons into the posterior pituitary. location of magnocelluar neurons
embryonic origin of posterior pituitary?
evagination of third ventricle so it is a neural extension
embyronic origin of anterior pituitary?
Rathke pouch (evagination of the roof of the pharynx) so its endothelial tissue
what 6 hormones are secreted by the anterior pituitary
Prolactin, TSH, GH, FHh, LH, ACTH (secretion is controlled by hypophysiotropic hormones)
What hormones are stored and released by posterior pituitary?
ADH (vasopressin) - water balance
Oxytocin - milk and uterine contractions (also role in bonding)
What is hypopituitarisum? (pituitary tumors)
compression of functional anterior pituitary tissue (often end up with more lactotrophs)
if posterior stalk is compressed -> diabetes insipidus
what is bitemporal hemianopsia? (pituitary tumors)
As dura is elevated, the lateral optic nerves are crushed.
what is the presentation of hyperprolactinemia due to a lactotroph adenoma?
amenorrhea, galactorrhea, loss of libido, and infertility.
Note: PRL inhibits GnRH secretion and directly impacts gonadal steriod production = infertility
what is the most common functional disorder (result from hormone secreting tumours)
PRL - prolactinoma 50%
GH - giantism (children) acromegaly (adults)
how could non-functional tumours lead to hypopituitarism? and what symptoms would result?
insufficient hormone production, affecting other hormones like
ACTH - adrenal insufficiency
TSH - hypothyroidism
FSH and LH - sexual dysfunction and infertility
if a patient presents with
- reduced bone mineral density
- increased abdominal fat
- decreased stamina
- hyperlipidemia
- depression
what is a reasonable mechanism?
trauma to somatotrophs of anterior pituitary resulting in hypopituitarism
-> reduced GH is causing all these symptoms (and is first in the hormonal sequence)
main differences in HPG axis in men and women in relation to feedback?
male - negative feedback from testosterone
female - negative or positive feedback
during which sleep phase is GH secreted?
slow wave sleep
what do magnocellular neurons secrete?
Vasopressin
what is the primary cause of increased mortality in patients with untreated acromegaly?
Cardiovascular and cerebrovascular disorders
which neuropeptide is a potent stimulus for the release of prolactin?
Thyrotropin-releasing hormone (TRH), oxytocin, vasoactive intestinal peptide
ACTH up regulates the activity of the side cleavage enzyme, resulting in:
increased conversion of cholesterol to pregnenolone (SCC is the rate limiting step)
