Hypothalamus and Pituitary Gland

Hypothalamus and Pituitary Gland

1. Hypothalamus

   • Hypothalamus is the small part of the ventricular system.
   • Adrenocorticotropic hormone
   • Thyroid Stimulating Hormone
     • Hypothalamus release Thyroid Releasing Hormone (TRH) to release thyroid stimulating hormone in anterior pituitary. The TSH is a thyrotropin and a large glycoprotein composed of a alpha and beta chain.
   • Gonadotropins: LH and FSH
     • Luteinizing hormone and Follicle stimulating hormone FSH: Spermatogenesis, Maturation of ovarian follicles and oestrogen LH: Testosterone, Ovulation, estrogen, progesterone (inhibit oxytocin)
   • Prolactin
     • Prolactin Releasing Hormone PRH is inhibited by PIH which is dopamine. Single chain protein closely related to growth hormone. Prolactin aids in production of milk.
   • Growth hormone
     • Growth hormone releasing hormone from hypothalamus, release IGF-1 and IGF-2. Generally increase in cell size (hypertrophy) and increase in cell number (hyperplasia).
     • IGF-1
       • Stimulates epiphyseal growth in long bones, hematopoiesis, ovarian steroidogenesis, myoblast proliferation and differentiation.
     • IGF-2
       • Stimulate tissue growth and organ growth, protein synthesis.

2. Pituitary

   • Highly innervated vascular system. It connects to the Hypothalamus and sits on a crevice on the skull. Comes in 2 lobes, one posterior and one anterior.
   • Posterior Pituitary
     • Extends from the down growth of neural tissues from the hypothalamus. Highly fenestrated capillaries
     • Oxytocin
       • 45% of the paraventricular nucleus secretes this and around 15% of the supraoptic nucleus secretes it. Oxytocin is known to aid in contraction of alveoli and expulsion of milk. It also helps the uterine muscle in rhythmic contraction. It may cause miscarriage or early birth if not suppressed by progesterone. For males: It is mainly shown when there are social connection.
     • Diuretic Hormone
       • As there is increased osmolarity, there is an increase in cellular volume, the osmoreceptors fire to act with the G-protein coupled receptors and the cAMP cascade to increase water reabsorption. Hence decreased osmolarity to complete the negative feedback
   • Anterior Pituitary
     • It is the upgrowth of the  epithelial cells. It is separate from the brain vertebrae. It carries the neurosecretory cells from the ventral hypothalamus.
     • Tropic hormones
       • The ventral hypothalamus release hormones for the anterior pituitary to the target tissues.