Physiology Flashcards
What is the command centre of the endocrine system?
hypothalamus-pituitary complex
What is the function of the hypothalamus-pituitary complex?
The complex secretes several hormones that directly produce responses in target tissues, as well as hormones that regulate the synthesis and secretion of hormones in other glands
What are the hormones produced by the posterior pituitary hormone?
ADH
Oxytocin
What is the target of ADH?
Kidneys, sweat glands, circulatory system
What is the effect of ADH?
Water balance
What is the target of oxytocin?
Female reproductive system
What is the effect of oxytocin?
Triggers uterine contraction during childbirth
What are the anterior pituitary hormones?
LH
FSH
TSH
PRL
GH
ACTH
What is the target of LH?
Reproductive system
What is the target of FSH?
Reproductive system
What is the target of TSH?
Thyroid gland
What is the target of PRL?
Mammary gland
What is the target of GH?
Liver, bone and muscles
What is the target of ACTH?
Adrenal glands
What are the effects of LH?
Stimulates production of sex hormones by gonads
What are the effects of FSH?
Stimulates production of sperm and egg
What are the effects of TSH?
Stimulates the release of thyroid hormone. TH regulates metabolism
What are the effects of PRL?
Promotes milk production
What are the effects of GH?
Induces targets to produce insulin-like growth factors. IGFs stimulate body growth and a higher metabolic rate
What are the effects of ACTH?
Induces targets to produce glucocorticoids which regulate metabolism and the stress ressponse.
How is prolactin secreted?
- The exception is prolactin, which is under tonic inhibition by hypothalamic dopamine (rather than controlled by an activating hormone)
- In a non-pregnant women, prolactin secretion is inhibited by prolactin-inhibiting hormone (PIH), which is actually the neurotransmitter dopamine, and is released from neurons in the hypothalamus
- Only in pregnancy do prolactin levels rise in response to prolactin-releasing hormone (PRH) from the hypothalamus
- Secretion of PRH regulated by a ‘short-loop’ negative feedback
- Effects of PRL mediated by the prolactin receptor
What are the usual pituitary tests?
TSH, fT4, LH, FSH, testosterone, GH, IGF-1, PRL
When is dynamic endocrine testing used?
- Hormone excess - suppression test
- Hormone deficiency - stimulation test
What is the stimulatory test for cortisol levels?
Synacthen (synthetic ATCH)
- Check cortisol at 0, 30 and 60 mins
- Normal: cortisol rises by 150 and reaches 500