Dr. Sanjoy Chakraborty

Endocrine System:

1. Pituitary Gland

Region / Hormone / Function
Posterior / Oxytocin / Stimulates uterine contraction during labor, stimulates the milk letdown reflex, and may play a role in promoting fertility.
Antidiuretic hormone (ADH) / Increases water re-absorption by the kidneys, and elevates blood pressure by increasing blood volume
Anterior / Gonadotropins (LH and FSH) / Stimulate sperm and ova development and stimulate secretion of sex hormones.
Growth hormone (GH) / Stimulate growth, protein synthesis, and lipid degradation.
Prolactin (PRL) / Stimulates mammary gland development and milk production.
Thyroid-stimulating hormone (TSH) / Stimulates the secretion of T3 and T4 from the thyroid.
Adrenocorticotropic hormone(ACTH) / Stimulate the secretion of glucocorticoids from the adrenal cortex.
Melanocyte stimulating hormone (MSH) / Role is obscure, but can stimulate melanocyte to darken skin.

2. Adrenal Gland

Location / Hormone / Function
Cortex / Zona glomerulosa / mineralocorticoids (aldosterone) / Increase renal resorption of sodium, bicarbonate, and water. Elevation of blood pH.
Zona fasciculata / Glucocorticoids (e.g. cortisol) / Increase stress tolerance and blood glucose, decrease inflammation.
Zona reticularis / Gonadocorticoids (androgens and estrogens) / provide each sex with the benefit of the hormones of opposite sex.
Medulla / Catecholamines (E and NE) / make the effects of sympathetic nervous system global and long lasting for ensured survival during immediate and extreme stress.

3. Hormones of pancreas.

Cell type / Hormone / Effect
Alpha / Glucagon / Increases blood glucose levels
Beta / Insulin / Decreases blood glucose levels.
Delta / GHIH (growth hormone-inhibiting hormone) / Inhibits secretion of insulin and glucagon.

Important points:

  1. There are four major ways of cell-cell communication.
  2. Paracrine factors are sometimes called local hormones.
  3. The nervous and the endocrine systems work together to regulate homeostasis.
  4. The endocrine is a slow-acting regulator.
  5. Endocrine glands do not have ducts and secrete their products into the interstitial space for transportation in the blood.
  6. Note that many glands have exocrine (have ducts) and endocrine functions. (e.g. pancreas)
  7. Target cells for hormone must have receptors.
  8. Receptors may be located on the cell surface or within the cell (cytoplasm or nucleus).
  9. Cell surface receptors act through 2nd messenger pathway.
  10. Important 2nd messengers are c-AMP, c-GMP, and Ca+2 ions.
  11. The pituitary gland is actually two independent glands attached together: the posterior pituitary or neurohypophysis and the anterior pituitary or adenohypophysis.
  12. The posterior pituitary is composed of modified nervous tissue. It does not make hormones; it stores and releases hormones made in the hypothalamus.
  13. Action potentials trigger the release of the posterior pituitary hormones.
  14. Anterior pituitary is under the control of releasing/inhibiting factors and hormones from the hypothalamus. These factors are delivered to the pituitary by a portal system.
  15. Anterior pituitary is composed of glandular tissue.
  16. Adrenal gland is actually two independent glands attached together; the adrenal cortex and the adrenal medulla.
  17. Adrenal cortex is constructed in three layers, each of which produces different category of hormones. The superficial layer, the zona glomerulosa, produces mineralocorticoids, such as aldosterone. The middle layer, the zona fasciculata, produces the glucocorticoids, such as cortisol. The innermost layer, the zona reticularis, produces the gonadocorticoids, such as the androgens and estrogen.
  18. Adrenal medulla is a sympathetic ganglion acting as an endocrine gland. It produces the catecholamines, epinephrine and norepinephrine.
  19. Thyroid gland lies anterior to the thyroid cartilage and consists of two lobes connected by a narrow stalk known as isthmus.
  20. Thyroid gland produces and stores the thyroid hormones (T3 and T4). It also produces calcitonin but does not store.
  21. Most of the thyroid hormones entering the bloodstream are attached to a special thyroid-binding globulins(TBG); rest attached to either transthyretin or albumins.
  22. Endocrine portion of pancreas is composed of pancreatic islets. Alpha cells produce glucagons, beta cells produce insulin, and the delta cells produce GHIH.
  23. Parathyroid glands are attached to the thyroid. They produce parathyroid hormone.
  24. Pineal gland is a modified nervous tissue; release melatonin, in response to darkness.