Discussion Question 1
The pituitary gland is called the “master gland” because it produces many hormones that regulate the activity of other glands in the endocrine system. Six distinct anterior pituitary hormones are all proteins, and in addition, pro-opiomelanocortin (POMC) has been isolated from the anterior pituitary. The posterior pituitary stores antidiuretic hormone (ADH) and oxytocin.
Anterior pituitary hormones consist of the growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTC), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin (PRL). GH targets the liver, muscle, bone, cartilage, and other tissues. It affects the anabolic hormone, which stimulates somatic growth, mobilizes fats, and spares glucose. TSH targets the thyroid gland and stimulates it to release thyroid hormones. ACTH targets the adrenal cortex which promotes the release of glucocorticoids and androgens. The ovaries and testes are target organs of FSH. In females, FSH stimulates ovarian follicle maturation and estrogen production. In males, FSH stimulates sperm production. LH also targets the ovaries and testes: in females, it triggers ovulation and stimulates ovarian production of estrogen and progesterone, and in males, LH promotes testosterone production. PRL targets breast secretory tissue which promotes lactation.
Posterior pituitary hormones include oxytocin and antidiuretic hormone (ADH). Oxytocin targets the uterus, which stimulates uterine contractions and initiates labor, and targets the breasts to initiate milk ejection. ADH, also known as vasopressin, targets the kidneys. ADH stimulates kidney tubule cells to reabsorb water.
All of these hormones secreted by the “master gland” are very important for maintaining homeostasis. Deficiencies and imbalances may cause disease and trauma.