HPA

Question 1

List all the hormones secreted via the hypothalamus and their respective features.

Answer 1

1. Corticotropin releasing hormone (CRH): Stimulates the release of ACTH.
2. Thyrotropin releasing hormone (TRH): Stimulates TSH and Prolactin secretion.
3. Growth hormone releasing hormone: Stimulates secretion of GH.
4. Somatostatin: Inhibits most hormone activity.
5. Gonadotropin releasing hormone (GnRH): Stimulates LH and FSH secretion.
6. Prolactin releasing hormone (PRH): Stimulates PRL secretion.
7. Prolactin inhibiting hormone (dopamine): Inhibits PRL secretion.

Question 2

What are the two hormones released from the posterior pituitary?

Answer 2

• Key role of PP is regulating fluid levels and aiding in reproduction.
• Oxytocin and ADH are produced by the paraventricular and supraoptic nerves respectively.
• They function as offsets of the hypothalamic neuron which is commonly called the hypothalamic - hypophyseal tract.
• Oxytocin stimulates lactation and aids in uterine contraction during partition.
• ADH aids in water reabsorption and vasoconstriction.
  -Binds to V2 receptors located on the basal surface of distal tubules of collecting duct. Initiates the Gs-cAMP-PKA pathway leading to the insertion of more aquaporin 2 channels to apical membrane increasing osmolarity.

Question 3

List the cell types present in the anterior pituitary, the hormones they secrete and their function.

Answer 3

1. Somatotrophs (GH and Somatostatin): Regulation of metabolic processes for growth + development.
   - Targets all tissues and the liver.
2. Corticotropes (ACTH): Adrenal cortex regulation as well as glucocorticoid synthesis and release.
   - Targets adrenal gland, adipocytes and melanocytes.
3. Lactotrophs (PRL): Mammary development in pregnancy, lactation for child suckling.
   - Breasts / Gonads.
4. Gonadotrophs (LH + FSH): LH stimulates oestrogen production in females and testosterone production in males. FSH stimulates ovulation in females and spermatogenesis in males.
   - Gonads.
5. Thyrotropes (TSH): Thyroid gland regulation and thyroid hormone synthesis + release.
   - Thyroid gland.