Pituitary and Hypothalamus: The Body’s Control Center

• Pituitary gland is a pea-shaped organ approximately 1.5 cm in diameter and is connected to the hypothalamus via a stalk called the infundibulum.
• The pituitary gland consists of two anatomical and functional portions: the anterior pituitary gland which constitutes 75% of the gland, and the posterior pituitary gland which constitutes the remaining portion.
• Hypothalamic cells produce and secrete at least nine different hormones.
• The pituitary gland secretes seven hormones: three trophic hormones (somatotrophs), three thyrotropic hormones (thyrotrophs), two gonadotropic hormones (gonadotrophs), and one lactotropic hormone (lactotrophs).
• Anterior pituitary hormones, or tropic hormones, stimulate the release of growth factors in liver, skeletal muscles, cartilage, bones and other tissues.
• Anterior pituitary hormones cause cells to grow and multiply by increasing the rate of gene expression.
• Anterior pituitary hormones enhance the breakdown of fats in adipose tissues.
• Anterior pituitary hormones release bursts of HGH every few hours, especially during sleep.
• Thyrotrophs secrete thyroid-stimulating hormone (TSH) which secretes triiodothyronine (T3) and thyroxine (T4).
• Thyrotrophs affect the metabolism.
• Gonadotrophs secrete female: follicle-stimulating hormone (FSH) and male: luteinizing hormone (LH).
• FSH stimulates the development of follicles in the ovary during the menstrual cycle each month and stimulates the production of estrogen in females.
• Ovulation is the release of the secondary oocyte in an ovary.
• Ovulation triggers progesterone production and helps prepare the uterus for a possible pregnancy.
• LH stimulates the production of testosterone.
• Lactotrophs secrete prolactin (PRL) which initiates and maintains the production of milk.
• Corticotrophs secrete adrenocorticotropic hormone (ACTH) or corticotropin which stimulates the cortex (outer portion) of the adrenal glands to secrete cortisol.
• Corticotrophs secrete melanocyte-stimulating hormone (MSH) which is present in amphibians and stimulates the dispersion of the pigment melanin in their melanocytes.
• Posterior pituitary hormones, or hypothalamic hormones, do not synthesize their own hormones.
• Oxytocin targets the uterus and breasts.
• Oxytocin stimulates the contractions of the smooth muscles of the uterus during the delivery of the baby and stimulates milk ejection.
• Vasopressin or antidiuretic hormone (ADH) allows the kidneys to absorb more water and decreases the amount of urine.
• Hypothalamic hormones are major controls to the secretions of the anterior pituitary gland.
• Thyrotropin-releasing hormone (TRH) releases TSH from the anterior pituitary.
• Prolactin-inhibiting hormone (PIH) aka dopamine inhibits the release of prolactin.