Hormones control their target organs. Some organ systems have their internal control systems along with, or instead of, hormones.

As we age, changes naturally occur in how body systems are controlled. Some target tissues become less sensitive to their controlling hormones. The amount of hormones produced may also change.

Blood levels of some hormones increase, some decrease, and some are unchanged. Hormones are also broken down more slowly.

Many of the organs that produce hormones are controlled by other hormones. Aging also changes this process. For example, an endocrine tissue may produce less hormone than it did at a younger age or produce the same amount at a slower rate.

The hypothalamus is located in the brain. It produces hormones that control the other structures in the endocrine system, including the pituitary gland. The amount of these regulating hormones stays about the same, but the response by the endocrine organs can change as we age.

The pituitary gland reaches its maximum size in middle age and gradually becomes smaller.

It has two parts:

• The back part stores hormones produced in the hypothalamus.

• The front part produces hormones that affect growth: the thyroid gland, adrenal cortex, ovaries, testes, and breasts.

The thyroid gland is located in the neck. It produces hormones that help control metabolism. With aging, the thyroid may become lumpy. Metabolism slows over time, beginning at around age 20.

The pancreas produces insulin. It helps sugar go from the blood to the inside of cells, which can be used for energy.

The average fasting glucose level rises 6 to 14 mg/dL every 10 years after age 50 as the cells become less sensitive to the effects of insulin. Once the level reaches 126mg/dL or higher, the person is considered to have diabetes.

The adrenal glands are located just above the kidneys. The adrenal cortex, the surface layer, produces the hormones aldosterone, cortisol, and dehydroepiandrosterone.

Aldosterone regulates fluid and electrolyte balance.

Cortisol is the stress response hormone. It affects the breakdown of glucose, protein, and fat.

Aldosterone release decreases with age. The decrease can contribute to lightheadedness and a drop in blood pressure with sudden position changes. Cortisol release also decreases with aging, but the blood level of this hormone stays about the same. Dehydroepiandrosterone levels also drop, but the effects of this drop on the body are not apparent.

The ovaries and testes have two functions. They produce reproductive cells (ova and sperm). They also produce sex hormones that control secondary sex characteristics, such as breasts and facial hair.

With aging, men often have a lower level of testosterone.

Women have lower levels of estradiol and other estrogen hormones after menopause.