The endocrine system consists of a group of glands and organs that regulate and control various body functions by producing and secreting hormones. Hormones are chemical substances that affect the activity of another part of the body. In essence, hormones serve as messengers, controlling and coordinating activities throughout the body. (See also Endocrine Glands.)
Levels of most hormones decrease with aging, but some hormones remain at levels typical of those in younger adults, and some even increase. Even when hormone levels do not decline, endocrine function generally declines with age because hormone receptors become less sensitive.
Some hormones that decrease with aging include
Estrogen (in women)
Testosterone (in men)
Growth hormone
In women, estrogen levels decline with menopause. In men, testosterone levels usually decrease gradually. Decreased levels of growth hormone may lead to decreased muscle mass and strength. Decreased melatonin levels may play an important role in the loss of normal sleep-wake cycles (circadian rhythms) with aging.
Hormones that usually remain unchanged or only slightly decrease include
Cortisol
Insulin
Thyroid hormones
Hormones that may increase include
Follicle-stimulating hormone
Luteinizing hormone
Parathyroid hormone
Some age-related hormonal changes may impact quality of life or cause bothersome symptoms (eg, hot flashes). Estrogen and progesterone therapy in menopausal women is discussed in Menopause. Testosterone replacement in older men is discussed in Effects of Aging on the Male Reproductive System.
