Hypothalamus & Pituitary Hormones Flashcards
where is the pituitary gland located?
sits in bony pocket at base of the skull, inferior to the hypothalamus
what are 4 notable structures of the pituitary gland?
hypophysial stalk
posterior pituitary
anterior pituitary
pars intermedia
what is the hypophysial stalk?
extension of the brain that attaches the pituitary gland to the brain
what is the posterior pituitary?
extension of the brain containing axons
neuronal secretion occurs here
what kind of cell makes up the anterior pituitary?
epithelial cells
what is the function of the pars intermedia?
separates anterior and posterior pituitary
what are the two major hormones secreted by the posterior pituitary?
vasopressin (antidiuretic hormone)
oxytocin
what is the function of ADH in the body?
conserves body water and regulates osmotic pressure of body fluids
how does ADH work to conserve body water?
acts on distal convoluted tubule and collecting ducts via cell surface receptors and cAMP formation, which enhances water permeability and rebabsoption
how does ADH get stimulated to conserve body water?
dehydration leads to an increase in osmolarity, which activates the osmoreceptor in brain and leads to ADH secretion
what condition arises when there is a deficiency in ADH?
central diabetes insipidus
what is central diabetes insipidus?
inability to retain water
excess thirst
frequent urination
what are some treatment options for central diabetes insipidus? how would they help?
drugs (clofibrate) to increase ADH secretion or to increase kidney response to ADH (chlorpropamide)
diuretics and dietary salt restriction to increase urine output
what happens when there is an excess of ADH?
excess water retention
headache
drowsiness
nausea
what are some treatment options for excess ADH and how do they help?
drugs (butorphanol) to decrease ADH secretion and reduce kidney response to ADH (demechlocycline)
what is the function of oxytocin in the body?
stimulates the contraction of smooth muscle cells (esp. mammary glands and uterus)
what two occasions causes oxytocin release and what results from this?
1) nursing - suckling reflex stimulates oxytocin release causing contraction of myoepithelial cells in breast to expel milk
2) child birth - oxytocin released during labour to stimulate rhythmic uterine contractions
what has oxytocin been used for clinically?
induce labour
therapeutically postpartum to decrease bleeding
what are 6 major hypothalamic hormones? what other hormones do they affect?
1) corticotropin releasing hormone (CRH) - increase ACTH
2) thyrotropin releasing hormone (TRH) - increase TSH and prolactin
3) gonadotropin releasing hormone (GnRH) - incr. LH and FSH
4) growth hormone releasing hormone (GHRH) - incr. GH
5) somatostatin - decrease GH
6) dopamine - decr. prolactin
what is the general feedback regulation of anterior pituitary hormones?
1) hypothalamus secretes releasing or inhibiting factor to pituitary gland (+ive or -ive)
2) pituitary gland releases hormone, which has positive impact on endocrine gland and negative impact on hypo.
3) endocrine gland releases tropic hormone, which positively impacts target tissue, negatively impacts hypo. and has a positive or negative effect on pit.
when is pulsatile/rhythmic secretion of hypothalamic and pituitary hormones higher at?
night time
what are 5 hormones released by ant. pituitary?
prolactin growth hormone TSH ACTH gonadotropins (LH/FSH)
where does prolactin work in the body?
breast to induce breast milk
where does growth hormone work in the body?
goes to liver, leading to secretion of IGF-1 which affect bone, soft tissues, and ultimately growth
where does TSH work in the body?
thyroid gland
releases T3 and T4 which affect many tissues and intermediary metabolism
where does ACTH work in the body?
adrenal cortex
releases cortisol which affect many tissues and intermediary metabolism
where do gonadotropins work in the body?
gonads
the affect sex steroids, gamete production, and ultimately sex characteristics/reproduction
what does a release of growth hormone do, specifically? (5pts)
decreases insulin sensitivity increases lipolysis increases IGF-1 secretion (affect protein synthesis and epiphyseal growth) increase protein synthesis increase bone growth
what stimulates GH secretion? what inhibits it?
stimulated by GHRH, hypoglycemia, exercise, certain AAs, and sleep
inhibited by somatostatin, IGF-1 (negative feedback), hyperglycemia
what is the feedback loop for GH secretion?
1) hypothalamus secretes somatostatin or GHRH, which have a negative impact and a positive impact on the pit. gland, respectively
2) pituitary gland releases GH (or inhibits it, depending on impact from hypo.)
3) GH has positive impact on liver and a +ive/-ive impact on body growth, lipolysis, glc uptake (depending on impact)
4) liver releases IGH-1 (impacts body growth, etc)
5) IGH-1 negatively impacts pit. gland and hypo.
what happens when there is an excess of growth hormone present?
somatotrope tumour
what condition occurs if GH excess occurs early in life?
gigantism (rare)
what condition occurs if GH excess occurs after body growth stopped?
acromegaly (excess soft tissue hyperplasia)
what are some treatment options for somatotrope tumour caused by excess GH?
tumour removal
SS analog
GH receptor antagonist
what conditions occur when there is a GH deficiency?
hypothalamic and pituitary lesions
could be tumour, injury, infection, congenital/genetic defects, that lead to GH deficiency
what does someone with GH deficiency look like?
proportional short stature, if it occurs early in life
what are symptoms of adult hypopituitarism? (6pts)
weakness fine wrinkling pale skin loss of sex drive genital atrophy menstrual cycle cessation
what are two other causes of retarded growth (GH is normal)?
GH receptor defect in target tissues (Laron Dwarfs)
IGF-1 deficiency (African pygmies)
what are some treatment options for GH deficiency?
GH and IGF-1 replacement
where is prolactin derived from?
lactotropes and somatomammotropes of ant. pit gland
what are 3 actions of prolactin in the body?
1) promote growth and function of mammary gland to induce milk production (and suckling reflex)
2) increases maternal behaviour
3) inhibits gonadotropin secretion/action on glands to decrease steroidogenesis
what controls the stimulation and inhibition of prolactin?
inhibited by dopamine
stimulated by oxytocin, TRH, VIP, and estrogen
what are the hormone changes that occur during the suckling reflex?
1) infant suckling causes mechanoreceptors in nipple to stimulate hypothalamus
2) hypothalamus acts on in two pathways: post. pit. gland and dopamine
a) posterior pit. increases oxytocin, which increases contraction of myoepithelial cells, leading to increased milk ejection
b) dopamine levels decrease, acting on ant. pit gland to increase prolactin and increase milk production
what condition occurs if there is an excess of prolactin?
hyperprolactinemia (most common form of pit. tumour)
what could cause excess prolactin?
DA receptor blockers
stress
high physical activities
under weight
what health consequences could occur to females due to excess prolactin?
anti-gonadal action causes secondary amenorrhea (Cessation of menstrual cycle) leading to infertility
what is galactorrhea?
inappropriate milk production
what health consequences could occur to males due to excess prolactin?
impotence
decreased sperm count
infertility
what is a treatment option for excess prolactin? how does it help?
DA agonists
suppress prolactin secretion and shrink prolactinomas