The hypothalamic-pituitary axis Flashcards
Pineal gland
located anterior to medulla above the third ventricle
functions as a third eye, light sensitive, and releases melatonin
promotes sleep
cyclic production over 24 hours
Hypothalamus
neuroendocrine glands secreting various tropic hormones from neurons into a portal circulatory system that delivers hormones to the anterior pituitary
Tropic hormones
hormones that act on other hormone secreting glands
Thyrotropin releasing hormone (TRH/TRF)
stimulates anterior pituitary to secrete TSH
Corticotropin releasing hormone (CRH/CRF)
stimulates anterior pituitary to secrete ACTH
Growth hormone releasing hormone (GHRH/GHRF/GRF)
works with somatostatin to work on the anterior pituitary to control GH production
Gonadotropin releasing hormone (GnRH/LHRH)
stimulates the anterior pituitary to secrete LH/FSH –> ovaries/testes
L for luteinizing
Dopamine (DA/PIH)
inhibits release of prolactin from anterior pituitary
prolactin stimulates the breasts to produce milk
Adenocorticotropic hormone (ACTH)
Target organ: Adrenal galnd
Synthesis of glucocorticoids
Follicle stimulating hormone (FSH)
Target organ: Ovaries/testes
Growth of reproductive system
Growth hormone (GH, HGH)
Target: liver, bone, adipose tissue
promotes growth, lipid and carbohydrate metabolism
Luteinizing hormone (LH)
Target: ovaries/testes
Sex hormone production
Prolactin (PRL)
Target: Ovaries, mammary glands
Secretion of estrogens/progesterone, milk
Thyroid stimulating hormone (TSH)
Thyroid gland
Secrertion of thyroid hormones
Hormones are produced by
Anterior pituitary by distinct cell types for each hormone
Tumors in the anterior pituitary can result in…
overproduction of the hormone derived from that tissue
Trans-sphenoidal surgery
through the nose
performed to remove the adenomas
Posterior pituitary gland
some neurons of hypothalamus have cell bodies in hypothalamus and axon termini in the posterior pituitary
ex. oxytocin and ADh are produced in the cell body and stored in posterior pituitary and later secreted in a regulated manner
Oxytocin
stimulates uterine contraction in females during childbirth
can be administered to induce labor
also stimulates release of milk from the breast
Anti-diuretic hormone (ADH)
acts on receptors in the kidney to promote translocation and insertion of water channels (aquaporins) into the PM of the renal collecting ducts
permits reabsorption of water by the kidneys –> more concentrated urine
stimulated by dehydration or low blood pressure
osmoreceptors in hypothalamus sense high osmolarity to stimulate ADH secretion
baroreceptors sense low blood pressure to stimulate ADH secretion from posterior pituitary
serum/urine osmolarity is measured by OSMOMETRY
Central Diabetes Insipidus
caused by damage to the hypothalamus or the pituitary
inadequate ADH secretion –> high serum osmolarity and low urine osmolarity
high urine output and thirst
can be treated with ADH analogs
Nephrogenic Diabetes Insipidus
results from an impaired ability of kidneys to respond to ADH
can be acquired, medication induced, or inherited
ADH level is usualy high
high serum osmolarity
low urine osmolarity with high urine volume output an thirst
Syndrome of inappropriate ADH secretion (SIADH)
overproduction of ADH
caused by some drugs, head injuries, ectopic production)
results in excess water reabsorption –> hyponatremia
concentrated urine
treated by removing underlying cause and fluid restriction
