Hypothalamus and Anterior Pituitary Structure and Function Flashcards
What are the endocrine functions of the hypothalamus?
The anterior pituitary lobe derives from fetal […] from the […] while the posterior pituitary lobe derives from fetal […] from the […]
Ectoderm
Roof of developing pharynx (Rathke’s pouch)
Neuroectoderm
Floor of developing ventricles
Describe the flow of blood in the hypophyseal portal system.
The pituitary receives blood from the […] and […] arteries which are branches of the […] artery.
Superior and inferior hypophyseal
Internal carotid
What is short loop and long loop feedback with respect to the neuroendocrine axes?
What are parvocellular neurons of the hypothalamus?
They secrete “releasing hormones” into the median eminance, which then travel via capillary bed to anterior pituitary causing AP to release hormones that enter general circulation and act in an endocrine fashion on distant tissues.
What is the hypothalamic pituitary adrenal axis?
Neural inputs from the SCN or the cortex due to circadian rhythms or stress synapse on the paraventricular nucleus and stimulate parvocellular neurons in PVN to release CRH and AVP into median eminence. CRH and AVP enter capillary bed via median eminence and travel to anterior pituitary. There they act on cells to stimulate the release of ACTH into the blood stream. ACTH (among other things) causes adrenal glands to secrete cortisol, which feeds back onto the hypothalamus and anterior pituitary in a negative fashion, inhibiting its own production.
What is the hypothalamic - pituitary - thyroid axis?
Parvocellular neurons in PVN and dorsomedial nuclei are stimulated to release TRH into median eminence. TRH enters capillary bed via median eminence and travel to anterior pituitary. There it acts on cells to stimulate the release of TSH into the blood stream. TSH causes thyroid to secrete T3 and T4 into blood to act on target tissues. T3 and T4 feed back onto the hypothalamus and anterior pituitary in a negative fashion, inhibiting their own production.
What is the hypothalamic - pituitary - gonad axis?
Parvocellular neurons in preoptic nucleus are stimulated to release Gonadotropin releasing hormone (GnRH) into median eminence. GnRH enters capillary bed via median eminence and travel to anterior pituitary. There it acts on cells to stimulate the release of luteinizing hormone (LH) and follicle stimulating hormone (FSH) into the blood stream.
- In females: LH and FSH cause ovaries to secrete estrogen and progesterone into blood to act on target tissues. They both also feed back onto the hypothalamus and anterior pituitary in a mixed fashion, can be inhibitory or stimulatory depending on where the female is in her cycle.
- In males: LH and FSH cause testes to release testosterone into blood to act on target tissues. Testosterone also feedsback onto anterior pituitary and hypothalamus to inhibit its own production.
What is the hypothalamic - pituitary - liver axis?
Parvocellular neurons in arcuate nucleus are stimulated to release growth hormone releasing hormone (GHRH) into median eminence. GHRH enters capillary bed via median eminence and travel to anterior pituitary. There it acts on cells to stimulate the release of somatostatin (SST) and growth hormone (GH) into the blood stream.
SST remains locally in pituitary and inhibits the release of GH. GH enters blood and stimulates release of IGF-1 from liver which promotes muscle and bone growth.
What role does the hypothalamus play in prolactin release?
Hypothalamus makes prolactin releasing factor (PRF) and thyroid releasing factor –> median eminence –> anterior pituitary –> release of prolactin –> act on target tissues (breast and ovaries)
Inhibited by dopamine
The adrenal cortex of the medulla secretes […] while the adrenal medulla secretes […]
Corticosteroids
Epinephrine and norepinephrine
What are magnocellular hypothalamic neurons?
These are neurons whose cell bodies are in the hypothalamus but whose axons project to the posterior pituitary directly via the infundibular stalk. Once in the posterior pituitary, they release hormones directly into the capillary beds of the posterior pituitary. As such, the molecules they secrete are NOT RELEASING FACTORS but are infact endocrine hormones because they travel through the bloodstream to reach their target tissues.
What are the hypothalamic and anterior pituitary hormones?
- What release and release inhibiting factors are secreted by hypothalamus?
- How do they get to anterior pituitary?
- What hormones are secreted by the anterior pituitary?
- What anterior pituitary hormone controls lactation? Would you expect it to be high or low?
- What processes can cause low prolactin levels?
- Release: GnRH, TRH, CRH, GHRH
Release inhibit: somatostatin, dopamine - Released from parvocellular neurons into capillaries in median eminence
- FSH, LH, TSH, ACTH, GH, Prolactin
- Prolactin; low
- High dopamine, inability of pituitary to produce prloactin, resistance at level of tissue
- What anterior pituitary hormone(s) control the menstrual cycle?
- Would you expect gonadotropins to be high or low?
- What processes can cause low levels of gonadotropins?
- FSH, LH
- Low
- Low GnRH, inability of pituitary to produce FSH and LH, resistance at level of tissue
- What anterior pituitary hormone controls metabolism and thermoregulation?
- Would you expect TSH to be high or low?
- What anterior pituitary hormone controls vascular tone?
- Would you expect ACTH to be high or low?
- TSH
- Low
- ACTH
- Low
In the case of the woman with low TSH, low ACTH, low FSH and LH, and low prolactin following postpartum hemorrhage, what is her syndrome called?
Sheehan Syndrome - pituitary gland grows a lot during pregnancy, if there is rapid blood loss during birth there can be a significant drop in blood flow to pituitary that can result in ischemic damage
What anterior pituitary hormone controls milk production?
Would you expect it to be low or high?
What can cause high levels of this hormone?
NOTE: Very high TRH can also cause release of prolactin
What process in anterior pituitary can cause bitemporal hemianopsia?
How can you account for her chronic headache?
WHat is the most likely diagnosis?
What is a pituitary adenoma?
What are symptoms of a prolactinoma?
