Pituitary Glands

Nota:

•  Embryologically, pituitary originate from different sources = a) Anterior pituitary from Rathke's pouch, an embryonic invagination of pharyngeal epithelium (explains the epithelioid nature of its cells), b) Posterior pituitary from neural tissue outgrowth of hypothalamus (explains the presence of glial-type cells).

1. Posterior pituitary aka neurohypophysis because hormones synthesized by hypothalamus
   1. ADH = Anti-Diuretic Hormone or Vasopressin

      Nota:

      • Pain, fear drugs = >ADH. Sweating, alcohol = <ADH.
      1. Vasoconstriction --> > BP and < GFR.
      2. > Aquaporin channels in distal convoluted tubules + collecting ducts --> > renal H2O reabsorption.
      3. > ACTH secretion --> > Cortisol
   2. Oxytocin
      1. Uterus smooth muscle contraction peri-labour for both delivery and uterus involution post-delivery.
      2. Mammary gland smooth muscle contraction promoting lactation.
2. Anterior pituitary aka adenohypophysis

   Nota:

   • Each hormone is talked about seperately except GH and Prolactin
   1. Corticotropin aka Adenocorticotropic hormone (ACTH) --> Adrenal gland secretion of Cortisol.
   2. Thyrotropin aka Thyroxine stimulating hormone (TSH) --> Thyroid gland secretion of T3 and T4 (thyroxine).
   3. Lutenizing hormone (LH) and Follicular Stimulating Hormone (FSH) -->
   4. Growth Hormone (Somatotropin)

      Nota:

      • Several factors related to a person's state of nutrition or stress are known to stimulate secretion: (1) starvation, especially with severe protein deficiency; (2) hypoglycemia or low concentration of fatty acids in blood; (3) exercise; (4) excitement; (5) trauma; (6) ghrelin, a hormone secreted by stomach before meals. Growth hormone also characteristically increases during the first 2 hours of deep sleep.
      1. Osteoblasts --> bones continue to become thicker throughout life (jaw bones, skull).
      2. > rate of protein synthesis in most cells (within minutes).
      3. > mobilization of fatty acids from adipose tissue (within hours); > free fatty acids in blood and use of fatty acids for energy (thus acting as a potent "protein sparer") + < rate of glucose utilization throughout body (conserves carbs).

         Nota:

         • &gt; blood levels of fatty acids above normal -&gt;  &lt; hepatic and skm sensitivity to insulin's effects on carbohydrate metabolism. &gt;GH = &gt;fat mobilization from adipose tissue --&gt; &gt;acetoacetic acid by liver released into body fluids --&gt; ketosis + fatty liver.
      4. Liver (and other tissues) form several small proteins = somatomedins [aka insulin-like growth factors (IGFs)] -> > all aspects of bone growth; similar to insulin on growth. Most important of these is somatomedin C (IGF-1)

         Nota:

         •  Pygmies of Africa + other dwarfs (e.g., Lévi-Lorain dwarf) have a congenital inability to synthesize significant amounts of somatomedin C, so although plasma concentration of GH is either normal or high, &lt; amounts of somatomedin C leads to small stature.
   5. Prolactin
      1. Develops mammary glands + produces milk.
      2. Inhibits fertility by inhibiting gonadotropins.
   6. B-endorphin
   7. B-lipotropin