The pituitary gland is one of the endocrine glands, about the size of a pea and found below the brain, and it produces various hormones for regulating metabolic processes. Posterior pituitary hormones that control growth and sexual maturation, such as human growth hormone and estrogen production, are the most commonly known hormones. Thyroid stimulating hormone is another hormone secreted by the pituitary gland that helps regulate metabolism and energy use. Another common hormone produced by the pituitary gland happens during and after pregnancy, and stimulates the production of human breast milk.
One of the most widely known hormones that is produced by the posterior pituitary gland is human growth hormone, and it is stimulated in early years during periods of rapid growth. Certain factors, such as deep sleep and intense physical activity, influence the rate at which human growth hormone is secreted by the pituitary gland. Reduced levels of posterior pituitary hormones such as human growth hormone can result in stunted growth and stature. Problems with the pituitary gland, which can be caused by a genetic abnormality or environmental substance, often lead to problems with height, specifically in growing children.
Other posterior pituitary hormones, like follicle stimulating hormone, have direct effects on the sexual maturation and healthy sexual function of both males and females. In females, follicle stimulating hormone stimulates follicles to release estrogens. In contrast to follicle stimulating hormone in females, spermatogonia is stimulated by the hormone to help produce healthy sperm in males. Lutenizing hormone is one of the other posterior pituitary hormones that is secreted during times of sexual formation, and this hormone acts on the male testes to help produce the sex hormone called testosterone.
Some hormones that are stimulated by the pituitary may only happen during certain phases in life, such as during bodily growth and pregnancy. Prolactin is one of the posterior pituitary hormones secreted during and after pregnancy, preparing the breasts to produce milk that is often used to nourish the newborn baby. During pregnancy, the hormone prepares the breasts for lactation so that after the baby is born, adequate milk can be produced to nourish the infant. Vasopressin is another common posterior pituitary hormone that acts on the collecting ducts of the kidney, aiding the reabsorption of water into the blood to reduce urine formation.