Trans-calcitriol or Calcitriol Impurity A, is the impurity of Calcitriol. Calcitriol is the hormonally active form of vitamin D, Calcitriol is the active metabolite of vitamin D3 that activates the vitamin D receptor (VDR). Calcitriol Impurity A is the physiologically active form of vitamin D. It is formed primarily in the kidney by enzymatic hydroxylation of 25-hydroxycholecalciferol (CALCIFEDIOL). Its production is stimulated by low blood calcium levels and parathyroid hormone. Calcitriol increases intestinal absorption of calcium and phosphorus, and in concert with parathyroid hormone increases bone resorption.

Norgestrel is synthetic steroidal progestin that is used in combination with ethinyl estradiol for oral contraception. Norgestrel is composed of a racemic mixture of two stereoisomers, dextronorgestrel and levonorgestrel. However, only the levorotary enantiomer (levonorgestrel) is biologically active. Norgestrel (and more specifically the active stereoisomer levonorgestrel) binds to the progesterone and estrogen receptors within the female reproductive tract, the mammary gland, the hypothalamus, and the pituitary. Once bound to the receptor, progestins like levonorgestrel will slow the frequency of release of gonadotropin releasing hormone (GnRH) from the hypothalamus and blunt the pre-ovulatory LH (luteinizing hormone) surge. Loss of the LH surge inhibits ovulation and thereby prevents pregnancy. Norgestrel in combination with ethinyl estradiol is indicated for the prevention of pregnancy in women who elect to use this product as a method of contraception.

Methyltestosterone is an anabolic steroid hormone used to treat men with a testosterone deficiency. It is also used in women to treat breast cancer, breast pain, swelling due to pregnancy, and with the addition of estrogen it can treat symptoms of menopause. The effects of testosterone in humans and other vertebrates occur by way of two main mechanisms: by activation of the androgen receptor (directly or as DHT), and by conversion to estradiol and activation of certain estrogen receptors. Free testosterone (T) is transported into the cytoplasm of target tissue cells, where it can bind to the androgen receptor, or can be reduced to 5α-dihydrotestosterone (DHT) by the cytoplasmic enzyme 5α-reductase. DHT binds to the same androgen receptor even more strongly than T, so that its androgenic potency is about 2.5 times that of T. The T-receptor or DHT-receptor complex undergoes a structural change that allows it to move into the cell nucleus and bind directly to specific nucleotide sequences of the chromosomal DNA. The areas of binding are called hormone response elements (HREs), and influence transcriptional activity of certain genes, producing the androgen effects. Methyltestosterone is marketed under the brand names Android, Androral, Metandren, Oraviron, Testred, Virilon.

Cholecalciferol (/ˌkoʊləkælˈsɪfərɒl/) (vitamin D3) is one of the five forms of vitamin D. Cholecalciferol is a steroid hormone that has long been known for its important role in regulating body levels of calcium and phosphorus, in mineralization of bone, and for the assimilation of Vitamin A. The classical manifestation of vitamin D deficiency is rickets, which is seen in children and results in bony deformities including bowed long bones. Most people meet at least some of their vitamin D needs through exposure to sunlight. Ultraviolet (UV) B radiation with a wavelength of 290–320 nanometers penetrates uncovered skin and converts cutaneous 7-dehydrocholesterol to previtamin D3, which in turn becomes vitamin D3. In supplements and fortified foods, vitamin D is available in two forms, D2 (ergocalciferol) and D3 (cholecalciferol) that differ chemically only in their side-chain structure. Vitamin D2 is manufactured by the UV irradiation of ergosterol in yeast, and vitamin D3 is manufactured by the irradiation of 7-dehydrocholesterol from lanolin and the chemical conversion of cholesterol. The two forms have traditionally been regarded as equivalent based on their ability to cure rickets and, indeed, most steps involved in the metabolism and actions of vitamin D2 and vitamin D3 are identical. Both forms (as well as vitamin D in foods and from cutaneous synthesis) effectively raise serum 25(OH) D levels. Firm conclusions about any different effects of these two forms of vitamin D cannot be drawn. However, it appears that at nutritional doses, vitamins D2 and D3 are equivalent, but at high doses, vitamin D2 is less potent. The American Academy of Pediatrics (AAP) recommends that exclusively and partially breastfed infants receive supplements of 400 IU/day of vitamin D shortly after birth and continue to receive these supplements until they are weaned and consume ≥1,000 mL/day of vitamin D-fortified formula or whole milk. Cholecalciferol is used in diet supplementary to treat Vitamin D Deficiency. Cholecalciferol is inactive: it is converted to its active form by two hydroxylations: the first in the liver, the second in the kidney, to form calcitriol, whose action is mediated by the vitamin D receptor, a nuclear receptor which regulates the synthesis of hundreds of enzymes and is present in virtually every cell in the body. Calcitriol increases the serum calcium concentrations by increasing GI absorption of phosphorus and calcium, increasing osteoclastic resorption, and increasing distal renal tubular reabsorption of calcium. Calcitriol appears to promote intestinal absorption of calcium through binding to the vitamin D receptor in the mucosal cytoplasm of the intestine. Subsequently, calcium is absorbed through formation of a calcium-binding protein.

Cholesterol is a sterol (a combination steroid and alcohol) and a lipid found in the cell membranes of all body tissues, and transported in the blood plasma of all animals. The high level of cholesterol in the blood is a marker of hypercholesterolemia, also called dyslipidemia. As a part of homeopathic product, it helps to support general liver and gallbladder health, and is used for temporary relief of symptoms related to adrenal glands such as fatigue and low energy. Cholesterol binds to and affects the gating of a number of ion channels such as the nicotinic acetylcholine receptor (nAChR) Inwardly-rectifying K+ channels (Kir); Transient receptor potential vanilloid 1 channels (TRPV1) and Large-conductance Ca2+-sensitive voltage-gated K+ channels (BK). It was shown the new mechanistic insights into the role of cholesterol in the regulation of nAChR, showing that cholesterol regulates the channels by two distinct mechanisms: stabilization of the channels in a resting state that depends on specific lipid-protein interactions and facilitation of the transitions between uncoupled and coupled states that depends on the hydrophobic thickness of the membrane

Mestanolone is an oral analogue of dihydrotestosterone. This steroid is a 17-alpha methylated form of this potent endogenous androgen, being essentially (in structure) to dihydrotestosterone what methyltestosterone is to testosterone. Overall, mestanolone has an activity profile not very dissimilar from the hormone it is derived from. Like dihydrotestosterone, mestanolone is primarily androgenic in nature, displaying a low level of anabolic activity. Both dihydrotestosterone and mestanolone are also devoid of estrogenic activity. Dihydrotestosterone was synthesized in 1935. After that 17-alpha-methylated version also appeared. This steroid was not frequently used in clinical medicine. It was produced under the name of ermalon for short period of time. Most studies involving mestanolone were carried out in the 1950s and 1960s. In the 1970s and 1980s it was used as part of the East German doping machine. Mestanolone was evaluated not for its anabolic ability but for its androgenic essence. It improved the functioning of the CNS and neuromuscular interaction. Athletes claimed that it did not make them huge, but gave them speed, strength, aggression, stamina and resistance to stress. Mestanolone is still valued as an oral androgen.