Bioidentical Hormone Replacement Therapy
Estrogens are a group of compounds named for their importance in the estrogen cycle of humans. The three major naturally occurring estrogens in women are estrone (E1), estradiol (E2), and estriol (E3). Estradiol is the predominant estrogen during the reproductive years, both in terms of absolute serum levels, as well as in terms of estrogenic activity. During menopause, estrone is the predominant circulating estrogen, while during pregnancy estriol is the predominant circulating estrogen in terms of serum levels. Although estriol is the most plentiful of the three estrogens, it is also the weakest, whereas estradiol is the strongest, with a potency of approximately 80 times that of estriol. Another type of estrogen called estetrol (E4) is produced only during pregnancy. All of the different forms of estrogen are synthesized from androgens, specifically testosterone and androstenedione by the enzyme aromatase.
Progesterone (P4) is a steroid hormone involved in the female menstrual cycle, pregnancy and embryogenesis of humans and other species. Progesterone exerts its primary action through the intracellular progesterone receptor. In addition, progesterone is a highly potent antagonist of the mineralocorticoid receptor. Progesterone has a number of physiological effects that are amplified in the presence of estrogen.
Testosterone is the principle male sex hormone, a steroid hormone from the androgen group that is found in mammals, reptiles, birds, and other vertebrates. In humans, testosterone is primarily secreted in the testicles of males and in the ovaries of females, although small amounts are also secreted by the adrenal glands. In men, testosterone plays a key role in the development of male reproductive tissues such as the testis and prostate as well as promoting secondary sexual characteristics such as increased muscle, bone mass, and the growth of body hair. In addition, testosterone is essential for health and wellbeing as well as the prevention of osteoporosis, muscle loss, and cognitive decline. In adult human males, on average, the plasma concentration of testosterone is about 7-8 times greater than the concentration of adult human females’ plasma, but as the metabolic consumption of testosterone in males is greater, the daily production is about 20 times greater in men. Females are more sensitive to the hormone.
DHEA also known as androstenolone or prasterone, is an important endogenous sex hormone. DHEA is the most abundant circulating steroid in humans, produced in the adrenal glands, the gonads, and the brain, where it functions predominantly as a metabolic intermediate in the biosynthesis of the androgen and estrogen sex steroids. DHEA also has a variety of important biological effects in its own right by binding to an array of nuclear and cell surface receptors and acting as a neurosteroid.
Growth Hormone (GH) is a peptide hormone that stimulates cell growth, reproduction and regeneration in humans. Growth hormone is a 191-amino acid, single chain polypeptide, synthesized, stored and secreted by the somatotroph cells within the lateral winds of the anterior pituitary gland. Growth hormone produced by recombinant DNA technology for medical use is abbreviated “HGH” in humans. Growth hormone is used as a prescription drug in medicine to treat children and adults with growth hormone deficiency syndromes.
Melatonin is also known chemically as N-acetyl-5-methoxytryptamine, is a naturally occurring compound found in animals, plants, and microbes. In humans, melatonin is secreted by the pineal gland, a small endocrine gland located in the center of the brain but outside the blood–brain barrier. Many biological effects of melatonin are produced through activation of melatonin receptors, while others are due to its role as a pervasive and powerful antioxidant, with a particular role in the protection of nuclear and mitochondrial DNA.
Thyroid Hormone, which is triiodothyronine (T3) and thyroxine (T4), are produced by the thyroid gland, which is primarily responsible for the regulation of metabolism. Iodine is necessary for the production of T3 and T4. The major form of thyroid hormone in the blood is thyroxine (T4), which has a longer half-life than T3. T4 is converted to the active T3 (three to four times more potent than T4) within somatic cells by deiodinases (5′-iodinase). Both T3 and T4 are used to treat thyroid hormone deficiency (hypothyroidism). They are both absorbed well by the gut, so can be given orally. Levothyroxine is the pharmaceutical name of physiological thyroxine (T4), which is metabolized more slowly than T3 and hence usually only needs once-daily administration. Natural desiccated thyroid hormones are derived from pig thyroid glands, and are a “natural” hypothyroid treatment containing 20% T3 and traces of T2, T1 and calcitonin. Also available are synthetic combinations of T3/T4 in different ratios (such as liotrix) and pure-T3 medications (liothyronine). Levothyroxine is usually the first course of treatment tried by conventional medicine. However, levothyroxine contains only T4 and is therefore largely ineffective for patients unable to convert T4 to T3. That is why some patients feel that they do significantly better only on desiccated thyroid hormones. These patients may choose to take natural thyroid hormone as it contains a mixture of T4 and T3. Desiccated thyroid is also used successfully in treatment of certain fibromyalgia and chronic fatigue syndromes.