Bradley Anawalt, MD
Susan Kirk, MD
Dorothy Shulman, MD
Several organs play a major role in helping the endocrine system to work well. Although these organs are not glands themselves, they do produce, store, and send out hormones that help the body to function properly and maintain a healthy balance.
Besides providing a connection between mother and fetus, the placenta is a special endocrine organ. It produces hormones that are similar to those produced elsewhere in the body. Human chorionic gonadotropin (hCG), estrogens, and progesterone are among the most important of these because they help maintain a normal pregnancy and prepare a woman's breasts for milk production and breastfeeding.
In a normal pregnancy, hCG stimulates the ovary to produce estrogens and progestins and helps stimulate normal development of the fetal genitals. The estrogens in the placenta stimulate breast development, promote normal labor, and help produce a steady rise in prolactin. The progestins stimulate breast development and help reduce uterine muscle contractions until the baby has fully developed. Human placental lactogen increases the amount of blood glucose and lipids (fatty substances) circulating in the mother's blood to ensure there is a food source for the developing baby.
Skin, Liver, and Kidneys
The skin, liver and kidneys work together to synthesize 1,25-diydroxyvitamin D (calcitriol), the active form of vitamin D, which helps maintain normal levels of calcium and phosphorus in the blood. In the skin, a molecule made from cholesterol is converted to vitamin D by exposure to ultraviolet rays from the sun. Vitamin D undergoes further chemical changes, first in the liver and then in the kidneys, to become calcitriol. Calcitriol acts on the intestine, kidneys, and bones to maintain normal levels of blood calcium and phosphorus.
Stomach and Small Intestine
The digestive tract is the largest endocrine-related organ system in the body. It makes and secretes several different types of hormones that play a role in the body's metabolism. Gherlin and leptin are two hormones that have been shown to regulate appetite and may be important in obesity and weight disorders.