The endocrine system is made up of organs and tissues that produce hormones. Hormones are chemicals produced in one location, released into the bloodstream, then used by other target organs and systems.

As we age, changes occur in the way body systems are controlled. Some target tissues become less sensitive to their controlling hormone. 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 (metabolized) 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 of its hormone than it did at a younger age, or it may produce the same amount at a slower rate.

The hypothalamus located in the brain 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 as we age. While the pituitary gland also located in the brain reaches its maximum size in middle age and then gradually becomes smaller. It has two parts:

1. The back (posterior) part stores hormones produced in the hypothalamus.
2. The front (anterior) part produces hormones that affect growth, the thyroid gland (TSH), 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 (nodular). Metabolism slows over time, beginning at around age 20. Because thyroid hormones are produced and broken down (metabolized) at the same rate, thyroid function tests are most often still normal. In some people, thyroid hormone levels may rise, leading to an increased risk of death from cardiovascular disease.

The parathyroid glands are four tiny glands located around the thyroid. Parathyroid hormone affects calcium and phosphate levels, which affect bone strength. Parathyroid hormone levels rise with age, which may contribute to osteoporosis.

Insulin is produced by the pancreas. It helps sugar (glucose) go from the blood to the inside of cells, where it can be used for energy.

The average fasting glucose level rises 6 to 14 milligrams per deciliter (mg/dL) every 10 years after age 50 as the cells become less sensitive to the effects of insulin.

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, and it has anti-inflammatory and anti-allergy effects.

Aldosterone release decreases with age. This decrease can contribute to lightheadedness and a drop in blood pressure with sudden position changes (orthostatic hypotension). Cortisol release also decreases with aging, but the blood level of this hormone stays about the same. Dehydroepiandrosterone levels also drop. The effects of this drop on the body are not clear. DHEA (dehydroepiandrosterone) increases energy and muscle strength, boosts immunity, decreases body weight. The body changes DHEA into two important sex hormones: testosterone and estrogen.Referred to as the "mother of all hormones" DHEA is the most abundant steroid hormone in the body. DHEA promotes the renewal and replacement of tissues and helps to maintain a healthy immune system. DHEA is also very active in the brain. It promotes neurotransmitter production, and so is crucial for maintaining both short term and long term memory. DHEA also plays an important role in keeping cortisol, the stress hormone balanced. In the young and healthy these hormones are balanced. However, as age progresses DHEA decreases while cortisol tends to increase, especially if any stressors are involved. High cortisol and low DHEA are serious risk factors for heart disease, diabetes, other diseases, obesity, and accelerated aging. Restoring low DHEA levels can have a positive effect on exhausted adrenal glands.

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

• With aging, men sometimes have a lower level of testosterone. (The average blood content in males is 692 mg/dL, or in the range of 376mg/dL to 1081 mg/dL (nanograms per decilitre) total).
  
  
• Women have lower levels of estradiol and other estrogen hormones after menopause. Estrogen and progesterone. Their are concerns that supplementation has adverse health effects but their are also health benefits. Progesterone is also important for females in relation to pregnancy. These two hormones are given to trans gender female people.
  

EFFECT OF CHANGES

Overall, some hormones decrease, some do not change, and some increase with age. Hormones that usually decrease include:

• Aldosterone
• Calcitonin
• Growth hormone - Human growth hormone (HGH) is considered the hormone of youth. It is responsible for the rapid growth and development of children and is also responsible for their astounding healing powers. In adulthood HGH becomes the repair and rejuvenation hormone. It also works throughout life to maintain brain function, muscle tone, bone strength, and the integrity of the skin and hair. IGF-1 or insulin-like growth factor-1 is another form of growth hormone, this one mainly manufactured and secreted by the liver, production and secretion of IGF-1 is triggered by growth hormone.
  
• Renin
• Melatonin is a hormone that is produced by the pineal gland in the brain. The pineal gland is the body's biological clock and melatonin plays a major role in the setting of this clock. Melatonin controls our sleep cycle and seasonal rhythms. In animals it controls mating and hibernation, and it is believed to help regulate the menstrual cycle in women. Melatonin is one of the most powerful antioxidants known. It fights cancer by acting as an intracellular antioxidant and is perhaps the only antioxidant that can penetrate every cell of the body. Melatonin also protects the immune system by fighting the effects of stress. It helps to counter the immune suppressing effects of cortisol. In humans melatonin levels are highest in children and decrease with age. Lower levels of melatonin signal the immune system to begin shutting down and also signal the endocrine system to produce fewer sex hormones. Alas, once we are past the reproductive phase of life we see a drastic decrease in melatonin and this decrease triggers the body to begin breaking down altogether, and we know where that eventually leads.

In women, estrogen and prolactin levels often decrease significantly.

Hormones that most often remain unchanged or only slightly decrease include:

• Cortisol
• Epinephrine
• Insulin
• Thyroid hormones T3 and T4, the thyroid gland releases several hormones. T3 (triiodothyronine) is the active form that enters the cell receptors. The storage hormone T4 (thyroxine) must be converted into T3 by the body in order to be used. Some people have trouble converting T4 into T3, especially those with illnesses and increased stress. Aging may also negatively affect this ability. T3 is the body's regulator and thermostat. It controls energy metabolism, regulating how much energy is stored as fat and how much is released into the bloodstream for use. The thyroid gland regulates your temperature, sleep patterns, digestive function, and is essential to the body's ability to fight infections and even mutant cells via the immune system. Thyroid hormone also plays an important role in maintaining healthy cognitive functions and mood.

Testosterone levels usually decrease gradually as men age.

Hormones that may increase include:

• Follicle-stimulating hormone (FSH)
• Luteinizing hormone (LH)
• Norepinephrine
• Parathyroid hormone