The endocrine and nervous systems work together to control almost all bodily functions. The nervous system acts quickly and precisely, while the endocrine system works more slowly. Together, these two systems work to keep your body in a steady state.
Endocrine glands throughout the body release chemical messengers called hormones. These hormones bind to receptors on target cells, where they produce a response. The same hormone may produce very different responses depending on the target cell with which it binds.
Hormones can bind to receptors on the outside or inside of cells. When hormones enter cells, they interact with DNA and regulate protein production. These proteins can be used to build new cell structures or make enzymes that regulate chemical reactions in your body.
The pituitary gland, sometimes called the master gland, sits at the base of the brain in close contact with a brain structure called the hypothalamus. Together, the hypothalamus and the pituitary control many of the endocrine functions in the body.
Just like a thermostat regulates temperature, if a hormone level gets too high, a negative feedback loop connected to the pituitary gland will down-regulate the hormone’s production. Conversely, if a hormone level gets too low, the opposite occurs, and the pituitary gland will send signals to increase the hormone’s production.
These feedback loops may lose some of their precision as you get older. The target organs may become less sensitive or produce less hormone. Hormone levels may also increase with aging as some hormones are more slowly broken down.
Genetic predisposition and environmental influences determine how each person’s endocrine system changes. The changes may not stay consistent, leading to hormonal fluctuations that bring symptoms associated with aging.
Perimenopause is a natural transition when female sex hormones, estrogen and progesterone, begin to decline. Ultimately, menstrual cycles and periods will end as the number of follicles in a woman’s ovary declines below a critical threshold. As estrogen levels decrease, women may notice symptoms associated with decreased estrogen, including:
Each woman is different, as are the symptoms she will experience. Although many women get through menopause without using supplements or medications, others need treatment to make the symptoms associated with plummeting hormone levels more manageable.
Men also experience a decline in sex hormones. Starting at around age 40, a man’s testosterone levels decline by about 1% each year. As a result, men do not go through the male-equivalent of menopause because they don’t experience the sharp decline in sex hormones that women do. However, even with this decline, only about 10% to 25% of men have a measurably low testosterone level.
When testosterone gets below a critical threshold, men may experience symptoms such as:
The rate of testosterone decline is not the same for all men. Because not all men experience symptoms associated with decreasing testosterone levels, many experts question whether the symptoms many men experience are directly related to decreasing hormone levels. Many men turn to medications and supplements to restore sexual function and improve physical performance to manage these symptoms.
Read More: Aging Differences by Sex and Gender
The pituitary gland is located at the base of the brain. The hypothalamus in the brain controls the six major peptide hormones that are produced in the anterior pituitary and control other endocrine glands throughout the body. The posterior pituitary stores vasopressin and oxytocin, two peptide hormones produced in the hypothalamus. The intermediate zone produces melanocyte-stimulating hormone.
Hormones produced by the pituitary gland and a summary of their effects:
|Growth hormone (GH)||Promotes growth of all body tissues.|
|Prolactin (PRL)||Promotes milk production in the mammary glands (breasts).|
|Thyroid-stimulating hormone (TSH)||Stimulates thyroid hormone release from the thyroid gland.|
|Adrenocorticotropic hormone (ACTH)||Stimulates hormone release from the adrenal gland, including cortisol and several androgens.|
|Follicle-stimulating hormone (FSH)||Stimulates gamete (egg and sperm) production in the ovary and testes.|
|Luteinizing hormone (LH)||Stimulates androgen production in the ovaries and testes.|
|Antidiuretic hormone (ADH)||Stimulates water reabsorption by the kidneys.|
|Oxytocin||Stimulates uterine contractions and milk letdown.|
|Melanocyte-stimulating hormone||Stimulates melanin production in the pigment-producing melanocytes.|
Growth hormone production declines with aging, which can cause:
Growth hormone declines are associated with the changes in body composition many people experience with aging, including weight gain and decreases in muscle mass and strength.
The pineal gland is a tiny gland at the base of the brain. While all of its functions are unknown, the pineal gland produces melatonin, a hormone that regulates your sleep-wake cycle. During the daytime, when there is a lot of light, melatonin secretion is inhibited. However, when light levels lessens at nightfall, melatonin secretion increases, and you become sleepy.
Melatonin levels decrease with age, which can cause sleep disturbances. Some medications compound this effect by suppressing melatonin even more. Decreasing melatonin levels may also affect the efficiency of the immune system.
The thyroid gland is a butterfly-shaped gland on the front of the neck. After being stimulated by TSH, the thyroid gland secretes some of its stored supply of iodine-containing hormones T4 (tetraiodothyronine, which is also known as thyroxine) and T3 (triiodothyronine), two hormones that control cellular metabolism. Thyroid hormone controls how much energy your body uses while at rest.
The thyroid gland also plays an important role in maintaining stable calcium levels. Parafollicular cells in the thyroid gland release calcitonin in response to increasing blood calcium levels. Excess calcium is stored in bone, which increases bone density and decreases blood calcium levels.
Both hypothyroidism (low thyroid) and hyperthyroidism (high thyroid) are more common with aging. The prevalence of mild or subclinical thyroid disease increases with age and affects 7% to 10% of women over the age of 60.
Autoimmune conditions also increase with age. Thyroid tissue antibodies are more common with increasing age. Antibodies that bind to thyroid tissue can cause increased or decreased thyroid hormone production.
The parathyroid glands are embedded on the posterior surface of the thyroid gland. These glands secrete parathyroid hormone when blood calcium levels are too low. Parathyroid hormone stimulates bone cells called osteoclasts. These cells break down bone and release calcium.
Excess parathyroid hormone secretion with aging may be associated with decreased bone density, which causes osteoporosis and compression fractures. However, decreasing estrogen and testosterone levels are primarily the causes of decreased bone density.
Learn more about the changes in your bones associated with aging by reading, “Do you get shorter as you age?”
The pancreas is an endocrine gland that produces hormones secreted into the blood and an exocrine gland that releases enzymes into the gastrointestinal tract to break down food. Endocrine cells include:
After you eat a carbohydrate-rich meal, blood glucose levels rise. The pancreas releases insulin, which shuttles glucose into body cells. Glucose is metabolized in body cells to produce energy. It can also be stored in the liver or muscles or converted to glycogen.
Aging is a risk factor, along with genetic predisposition, race, and increased body mass, for type 2 diabetes. Aging body cells become more resistant to the effects of insulin. Beta cells in the pancreas may also become less sensitive to blood glucose levels.
As body cells become more resistant to the effects of insulin, the pancreas responds by increasing insulin production and release. Eventually, the beta cells can no longer keep up, and blood glucose rises. High blood glucose levels damage the inner lining of small blood vessels, increasing the risk of cardiovascular disease.
In many cases, type 2 diabetes can be improved and even reversed by increased physical activity and moderate weight loss.
The adrenal glands are located on the top of the kidneys. The adrenal glands have an inner medulla and an outer cortex. The adrenal cortex is divided into regions:
The adrenal medulla produces the sympathetic hormones epinephrine and norepinephrine. These hormones have many functions, including:
Changes in aldosterone production with aging can contribute to lightheadedness and decreased blood pressure with standing.
The primary hormones produced by the ovaries are estrogen and progesterone, although the ovaries also produce androgens. Estrogen and progesterone stimulate the development of the female secondary sex characteristics, prepare the female body for childbirth, and regulate the menstrual cycle.
The primary hormone produced by the testes is testosterone, a hormone that has both androgenic and anabolic effects. Testosterone stimulates and maintains the male secondary sex characteristics and regulates the production of sperm.
Outside the testes, testosterone is converted to dihydrotestosterone (DHT) by the enzyme 5-alpha reductase. Hair follicles are sensitive to DHT. Increased testosterone and stress hormones can affect the hair follicle, increasing the risk that men will turn gray and lose hair. Medications, such as finasteride, reduces hair loss and stimulates hair regrowth by blocking 5-alpha reductase, which reduces the amount of testosterone converted to DHT by up to two-thirds.
If you are experiencing any of the changes associated with hormonal aging, contact one of the medical professionals at Invigor Medical to learn more about potential treatment options.
While we strive to always provide accurate, current, and safe advice in all of our articles and guides, it’s important to stress that they are no substitute for medical advice from a doctor or healthcare provider. You should always consult a practicing professional who can diagnose your specific case. The content we’ve included in this guide is merely meant to be informational and does not constitute medical advice.