Aging changes in hormone production
Information:
BACKGROUND
The endocrine system is made up of organs and tissues that produce hormones. The hormones are produced in one location, secreted into the bloodstream, and then used by certain other "target" organs and system. The hormones control the target organs. Some organ systems have their own internal control systems instead of, or in addition to, hormones.
With aging, changes occur in the way that body systems are controlled. Some target tissues become less sensitive to their controlling hormone. The amount of hormones produced can change. Blood levels of some hormones increase, some decrease, and some are unchanged. Hormones are also broken down slower.
Many of the organs that produce hormones are, in turn, controlled by other hormones. Aging also changes this process. For example, an endocrine tissue may produce less of its hormone when it is stimulated, or it may produce the same amount but at a slower rate.
AGING CHANGES
The hypothalamus is located in the brain. It produces hormones that control the other structures in the endocrine system. The amount of these regulating hormones stays about the same, but the response by the endocrine organs can change with aging. For example, a hormone called TRH makes the thyroid gland produce thyrotropin (TSH). In women, the amount of TSH produced stays the same, but in aged men it may be less.
The pituitary gland is also located in the brain. It has two parts. The back (posterior) portion stores hormones produced in the hypothalamus. The front (anterior) portion produces hormones that affect the thyroid gland, adrenal cortex, ovaries, testes, and the breasts (in women). This gland reaches its maximum size in middle age and then gradually becomes smaller.
The thyroid gland in the neck produces hormones that help control metabolism. With aging, the thyroid often becomes lumpy (nodular). The basal metabolic rate (BMR) gradually declines beginning about age 20. Less thyroid hormone may be produced, but there is also less body mass (because of loss of muscle and bone tissue) so thyroid function tests usually remain within the normal range. Calcitonin is also produced by the thyroid; its level may be reduced.
The parathyroids are 4 tiny glands located around the thyroid. The hormone produced by these glands affects calcium and phosphate levels. This, in turn, affects the strength of the bones. Changes in the level of parathyroid hormones may contribute to osteoporosis.
Insulin is produced by the pancreas. Insulin "fits" into a place on the cell wall called an insulin receptor site. It acts like a "lock and key" to help blood sugar (glucose) get from the blood to the inside of cells, where it can be used for energy. As you age, your pancreas may begin producing less insulin. Usually, though, insulin production continues at the same rate. In spite of this, the "normal" or "average" fasting glucose level rises 6 to 14 mg/dl (milligrams per deciliter) for each 10 years after age 50. This is because the cells become less sensitive to the effects of insulin (probably because of a loss in the number of insulin receptor sites in the cell wall).
The adrenal glands are located just above the kidneys. The adrenal cortex is the surface layer. It produces the hormones aldosterone and cortisol. Aldosterone regulates fluid and electrolyte balance. Cortisol is the "stress response" hormone. It affects the breakdown of glucose, protein, and fat, and has anti-inflammatory and anti-allergy effects. Aldosterone secretion decreases with age, which can contribute to light-headedness and drop in blood pressure with sudden position changes (orthostatic hypotension). Cortisol secretion decreases, but the level stays about the same. This is because the slows the breakdown or cortisol when the level starts to fall.
The ovaries and testes have 2 functions. They produce the sex hormones (those that control secondary sex hormones such as facial hair). they also produce the reproductive cells (ova and sperm). With aging, men MAY experience a slightly decreased level of testosterone. Women have decreased levels of estradiol and estrogen after menopause.
EFFECT OF CHANGES
Overall, some hormones are decreased, some unchanged, and some increased with age. Hormones that are usually decreased include aldosterone, renin, estrogen (in women), calcitonin, prolactin (in women), and growth hormone. Hormones that remain unchanged or only slightly decreased include the thyroid hormones T3 and T4, cortisol, insulin, testosterone (in men), epinephrine, parathyroid hormone, and 25-hydroxyvitamin D. Hormones that may be increased include follicle-stimulating hormone (FSH), leutinizing hormone (LH), and norepinephrine.
RELATED TOPICS.
aging changes in immunity
aging changes in organs, tissues, and cells
aging changes in the female reproductive system
aging changes in the male reproductive system
menopause
(Picture: endocrine table 1; endocrine table 2)
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