Pituitary Gland: It is also called as Hypohysis. It is located in a saddle-shaped space in the Sphenoid Bone called the Sella Tursica which is located in the base of the brain in the frontal lobe.
The hormones secreted by the Pituitary are either secreted by the Hypothalamus or are stimulated by the hormones secreted by the Hypothalamus for ex: Thyrotropin-releasing hormone which stimulates the release of TSH.
Hypothalamus is a tiny part of the brain which is attached to the pituitary gland by means of the infundibular (hypophyseal) stalk. Hypothalamus is considered as the “Master controller” or “Master gland” as its main function is:
- Releasing Hormones
- Inhibiting Hormones
Pituitary Gland is one of the major and most important organs in the human body, although small in size (Size of a Pea) it is very important in function as the hormones produced from the gland travel throughout the body and are either responsible for the function of certain organs like (TSH helps in producing Thyroid gland to produce T3, T4 etc) or helps in stimulation certain functions in the body.
Pituitary Gland is divided into 2 parts:
- Anterior Pituitary
- Posterior Pituitary
Hormones Secreted by Anterior Pituitary:
- Adrenocorticotropic hormone (ACTH)
- Thyroid Stimulating Hormone (TSH)
- Follicle Stimulating Hormone (FSH)
- Lutenizing Hormone (LH)
- Growth Hormone (GH)
Hormones secreted by the Middle lobe of Pituitary:
- Melanocyte Stimulating Hormone or Intermedins
Hormones Secreted by the Posterior Pituitary:
- Oxytocin (OT)
- Antidiuretic Hormone or Vasopressin (ADH)
Hormones Secreted by Pituitary Glands and their Functions:
1. Thyroid stimulating hormone (TSH) or Thyrotropin: This hormone which is secreted by the anterior lobe of the pituitary.
- TSH acts on the Thyroid gland to release Thyroxine (T4) and Triiodothyronine (T3) which “Regulates Body Metabolism”
- Hypothalamus secretes Growth Hormone inhibiting hormone (GHIH) to inhibit the secretion of TSH.
2. Growth hormone (GH): Growth Hormone is also called as (hGH – Human Growth Hormone) or Somatotrophin. Growth hormone is released by the Anterior Pituitary.
- Growth hormone stmulates the Special Liver cells which produce somatomedin-C, which is critical for the growth of all body tissues.
- It assists with the movement of amino acids into tissue cells and the transformation of amino acids into proteins that the body requires.
- It aids in the release of fatty acids from adipose (fat) tissue so that they can be used for energy.
- Growth Hormone helps to regulate blood nutrient levels after eating and during periods of fasting.
- When sufficient amounts of Growth Hormone has been released the hypothalamus secretes GHIH (Growth Hormone Inhibiting Hormone) which inhibits the further release of growth hormone.
3. Prolactin (PRL): It is secreted by Anterior lobe of Pituitary.
- Prolactin hormone stimulates milk production in women following pregnancy.
- Men secrete Prolactin whose function is not known yet.
- Stimulates breast milk production and controls menstrual periods following pregnancy.
4. Adenocorticotrophic Hormone (ACTH) or Corticotropin: It is secreted by the Anterior Lobe of Pituitary.
- ACTH Stimulates the adrenal cortex to produce glucocorticoids like Steroid “Cortisol” which play a vital role in metabolizing carbohydrate.
- ACTH has melanocyte stimulating properties that can increase skin pigmentation.
5. Follicle Stimulating Hormone (FSH): FSH stimulates the growth and secretion of Ovarian Follicles in women and the production of Sperm in men.
6. Luteinizing Hormone: Stimulates Ovulation and formulation of the Corpus luteum in females. In males, LH is called (Interstitial cell stimulating hormone -ICSH) which influences the secretion of testosterone and other sex hormones from the specialized area in the testes.
7. Anti Diuretic Hormone or Argenine Vasopressin: It is a hormone secreted by the Posterior Pituitary.
- It is a peptide hormone produced by the magnocellular cells of the hypothalamus.
- Increased osmolarity stimulates the secretion of ADH from the posterior pituitary.
- ADH acts in increasing blood pressure
- ADH increases water resorption
- Disruption of ADH causes Syndrome of inappropriate ADH (SIADH)
8. Melanocyte Stimulating Hormone or Intermedins: It is secreted by the Middle Lobe of Pituitary.
- MSH stimulates the release of melanin (melanogenesis) by melanocytes in the skin and hair.
- MSH has certain effects on the Appetite and Sexual Arousal.
- MSH is the main cause of color of the skin in Humans.
- MSH levels increase in females during Pregnancy.
9. Oxytocin: It is a hormone secreted by Posterior Pituitary.
- Main function is Uterine Contractions before and after birth which acts during the 2nd and 3rd stages of Labor.
- Oxytocin is released during breast feeding during the first few weeks of lactation.
- Helps in controlling Social behavior
- Oxytocin helps in Wound healing
- Prepare the Fetus for Delivery
- Known to be the reason behind Romantic Attachments
Gonadotrophic hormones: Luteinizing Hormones and Follicle Stimulating Hormone are called as Gonadotrophic Hormones as they influence and act on the gonads (reproductive organs).
Hormones which stimulate the Pituitary Gland to Secrete its 6 hormones:
Thyrotropin Releasing Hormone: This hormone which is released from the Hypothalamus Stimulates the anterior lobe of pituitary gland to secrete the Thyroid Stimulating hormone.
Growth Hormone Releasing Hormone (GRH or GHRH): It is the hormone secreted by the hypothalamus which stimulates the release of Growth Hormone from the Anterior pituitary.
Prolactin Releasing Hormone (PRH): It is secreted by Hypothalamus which stimulates the secretion of Prolactin from the anterior Pituitary gland.