Human growth hormone, also known as somatotropin, is the most abundant hormone made by the pituitary gland in the brain. Cells in the pituitary, known as somatotropes, produce HGH and release it into the bloodstream, where it can have a direct effect by itself on tissues and organs, or it can be absorbed by the liver and converted into various other growth factors.
HGH is released in pulses throughout the day, determined in large part by “circadian rhythms.” Most HGH release occurs during stages III and IV deep sleep.
Human Growth Hormone obtained its name from the fact that HGH is necessary to make children grow in stature. At one time, this was believed to be essentially the only role played by HGH. We now know differently. It appears that nearly every organ in the body depends on Human Growth Hormone for proper growth and development as it increases anabolic activity and lean body mass. It regulates the body’s metabolism of proteins, electrolytes, carbohydrates, and controls how the body uses fat.
HGH has been called a master hormone because of its ability to affect all the other hormones and organs throughout the body. It has repairing and restorative abilities which can reverse the damage, and facilitate re-growth of failing organs somewhat, something no other hormone can do. It is unclear, however, whether maintaining physiologic levels of HGH or IGF-1 equivalent to those of a 25- to a 35-year-old person will extend the length of human life. But it is worth noting that the Journal of Clinical Endocrinology and Metabolism reported in 1997 that healthy centenarians have high serum IGF-1 concentrations.
Human Growth Hormone levels decline with age. After the age of 25, levels begin to decline at a rate of 10 – 15% per decade. As the levels of growth hormone decrease with age, so do the levels of IGF-1, falling by nearly 50% after the age of 40. The decline in HGH is known as somatopause.
Every hormone has a ‘pause’ and human growth hormone is no different.
(©Gregory W. Petersburg, D.O. All rights reserved. Living Younger, pp. 183-184.)
DHEA levels decrease progressively from a peak at age 25 to less than 20% of that peak before the age of 70. Many people over the age of 40 produce inadequate levels of DHEA. Levels are typically low in those with chronic diseases such as obesity, diabetes, deficiencies, cancer, high blood pressure, heart disease and AIDS. Elevated insulin levels decrease DHEA levels; one reason why hyperinsulinemia increases vascular disease.
(©Gregory W. Petersburg, D.O. All rights reserved. Living Younger, pg. 139.)
Melatonin is produced naturally in the body, by the pineal gland in the brain. It is a fundamental regulator of the body’s inner clock, or circadian rhythm, which determines the 24-hour sleep/wake cycle. Levels are higher at night, are suppressed by bright light, and decline as we age. The length and height of the melatonin peak at nighttime determines the circadian phase of the biological clock and governs vital body parameters such as the variation of hormone levels, body temperature and sleep-wake cycles. Hormones such as estrogens, testosterone, DHEA, growth hormone, and cortisol are subject to circadian fluctuations. Over 100 body functions fluctuate over a 24-hour period and are dependent on sunlight and darkness as cues.
Melatonin derives from the essential amino acid L-tryptophan. Tryptophan, consumed in foods we eat (especially turkey and milk), is converted into the neurotransmitter serotonin, and is then further metabolized into melatonin at night. Melatonin levels are higher at night because bright light suppresses melatonin production.
The pineal gland is important, for not only producing melatonin but it also helps in restoring the thymus gland. The thymus gland, located in the upper chest, is a player in immune function by producing T-cells and natural killer cells. Unfortunately, the thymus begins to shrink drastically after about the age of 12. Because of the pineal gland’s direct effect on the thymus gland, replenishing adequate melatonin levels may improve immunity.
As we age, melatonin levels decrease. That is one reason why older people sleep less, even though they need the same amount of sleep as they did when they were younger adults. By about the age of 45 the pineal gland runs down. While melatonin secretion slowly declines over many years, in middle age the hormone level plummets.
(©Gregory W. Petersburg, D.O. All rights reserved. Living Younger, pg. 141.)
Pregnenolone is a hormone produced in the mitochondria in the brain, gonads and the adrenal glands. It is derived from cholesterol, is a precursor for the biosynthesis of steroid hormones.
Pregnenolone has been called the mother of hormones because it is the precursor hormone to cortisol, progesterone and to DHEA, which is a precursor to the sex hormones testosterone and estrogen. Pregnenolone can be found in greater concentrations in the brain than in any other organ in the body and serves to enhance all our mental functions. As we age pregnenolone levels decline in the body as much as 60% by the time we are 75 years old.
On its own pregnenolone is essential to keeping brain function at its peak capacity. However, male and female bodies use pregnenolone differently. In women, more of the pregnenolone becomes estrogen while in men more is used to make testosterone. For this reason, men with prostate conditions should use pregnenolone with caution. Pregnenolone replacement can raise progesterone levels in women as well.
Memory enhancement has been observed in humans and animals when given pregnenolone. Pregnenolone reinforces neurotransmitter systems that decline with age. It stimulates release of acetylcholine in the hippocampus of the brain, facilitating memory processes. It may also be an important component in repairing the fatty layer that protects nerves, known as the myelin sheath. Pregnenolone may also have a protective action against the unwanted effects of elevated levels of cortisol, our stress hormone. There as yet unsubstantiated claims that pregnenolone is useful in some forms of cancer and arthritis, in degenerative diseases associated with aging in general and in obesity. Current research is being done to test pregnenolone’s ability to help those suffering from Alzheimer’s disease, multiple sclerosis, cardiovascular problems and for boosting the immune system.
Because pregnenolone is a precursor hormone to estrogen and testosterone, those with prostate, breast and uterine cancer should avoid pregnenolone replacement.
There are no reported major adverse effects from the supplementation of pregnenolone. Minor side effects have an incidence of less than 1% and include headache, bloating and nausea, heartburn, acne, sense of agitation, sedation.
There have been no reported significant effects on the hormones that are derived from pregnenolone, even in high doses. Nevertheless, conversion to DHEA could theoretically cause acne and hair loss, especially in women
If any of these symptoms occur, discontinue the pregnenolone for one week or until symptoms resolve and notify your physician, then resume at one-half the previous dose.
(©Gregory W. Petersburg, D.O. All rights reserved. Living Younger, pp. 145-146.)
The thyroid gland is located in the neck, below the larynx, known as the voice box. The thyroid gland affects every function in the body because it controls metabolism.
Thyroid hormones regulate the entry of oxygen into the cells, thus controlling metabolic rate, body temperature, brain maturation in neonates, heart rate, hair growth, ovulation, skin turnover, growth and development. Additionally, thyroid increases protein synthesis.
stimulating hormone (TSH) is produced by the pituitary gland in the brain and stimulates the thyroid gland to produce T4 (thyroxine). T4 is the primary hormone secreted from the thyroid gland. The liver and other tissues convert most of it to T3 (triiodothyronine), the more active form. T4 crosses the blood-brain barrier, but T3 does not. Some T4 also converts to metabolically inactive Reverse T3, more so with age.