Flashcards in Endocrine - Hypothalamus & Pituitary Deck (28)
What 2 hormones are released by the posterior pituitary?
1. vasopressin (ADH, antidiuretic hormone)
Why is vasopressin released?
to conserve body water and regulate osmotic pressure of body fluids
How does the body know to release vasopressin?
dehydration leads to an increase in osmolarity which activates osmoreceptors in the brain and vasopressin secretion
What is the target organ of vasopressin?
kidney cells, specifically distal convoluted tubule and collecting ducts via cell surface receptors and cAMP formation; enhances water permeability and reabsorption
what happens when you are deficient in ADH?
central diabetes insipidus - inability to retain water, excess thirst, frequent urination
What drug can you use to treat deficient ADH?
1. clofibrate - increase ADH secretion
2. chlorpropamide - increase kidney response to ADH
what happens when there is an excess of ADH?
- water retention
what drugs can you use to treat Excess ADH?
1. Butorphanol - decrease ADH secretion
2. demechlocycline - reduce kidney response to ADH
What does oxytocin do?
- stimulates the contraction of smooth muscle cells: mammary glands and uterus.
- suckling reflex when nursing stimulates oxytocin release
- released during labour to stimulate rhythmic uterine contractions
The release of growth hormone is stimulated by
- certain amino acids
the release of growth hormone is inhibited by
- IGF-1 (-ve feedback)
What are the effects of growth hormone?
- stimulates release of IGF-1 from the liver and increases lipolysis, protein sun these and epiphyseal (bone) growth
- also decreases insulin sensitivity and decreases glucose uptake
what conditions could occur when there is a somatotrope tumor that causes an excess of GH?
1. gigantism (early in life)
2. acromegaly (GH excess after body has stopped growing)
what are ways to treat conditions caused by increased/excess GH?
1. tumor removal
2. SS analogs
3. GH receptor antagonist
abnormal Gh receptors that are unresponsive to hormone. Symptoms resemble those of severe GH deficiency even though GH levels in the blood are high
what can cause deficiency in GH?
- GHRH deficiency
- pituitary lesions (tumor, infection, defects)
what does release of prolactin do?
- promotes growth & function of mammary gland-milk production
- increased maternal behaviour
- inhibits gonadotropin secretion
how is prolactin controlled?
inhibited by hypothalamic dopamine
what stimulates prolactin release?
the suckling reflex stimulates what?
- release of oxytocin from the posterior pituitary
- decrease of dopamine in hypothalamus resulting in prolactin release from anterior pituitary
inappropriate milk production due to excess prolactin release
what can cause excess prolactin release ?
2. dopamine receptor blockers (from psychiatric medications)
3. hyperprolactinemia- caused by adenomas and lactotropes
what happens in males when there is an excess of prolactin?
- decreased sperm count
how can excess prolactin release be treated?
dopamine agonists which suppress prolactin secretion and shrink prolactinomas
what is the action of LH?
stimulates estrogen, progesterone and testosterone
What is the action of FSH?
stimulates ovarian follicles and sperms
what hormones stimulate FSH and LH release?
- estrogen (high level)