17β-Dihydroequilin

17β-Dihydroequilin

17β-Dihydroequilin

Chemical compound

Not to be confused with 17α-Dihydroequilin, 17α-Dihydroequilenin, or 17β-Dihydroequilenin.

17β-Dihydroequilin is a naturally occurring estrogen sex hormone found in horses as well as a medication.[1][2] As the C3 sulfate ester sodium salt, it is a minor constituent (1.7%) of conjugated estrogens (CEEs; brand name Premarin).[1] However, as equilin, with equilin sulfate being a major component of CEEs, is transformed into 17β-dihydroequilin in the body, analogously to the conversion of estrone into estradiol, 17β-dihydroequilin is, along with estradiol, the most important estrogen responsible for the effects of CEEs.[1]

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Pharmacology

Pharmacodynamics

17β-Dihydroequilin is an estrogen, or an agonist of the estrogen receptors (ERs), the ERα and ERβ.[1] In terms of relative binding affinity for the ERs, 17β-dihydroequilin has about 113% and 108% of that of estradiol for the ERα and ERβ, respectively.[1] 17β-Dihydroequilin has about 83% of the relative potency of CEEs in the vagina and 200% of the relative potency of CEEs in the uterus.[1] Of the equine estrogens, it shows the highest estrogenic activity and greatest estrogenic potency.[1]

Like CEEs as a whole, 17β-dihydroequilin has disproportionate effects in certain tissues such as the liver and uterus.[1] Equilin, the second major component of conjugated estrogens after estrone, is reversibly transformed into 17β-dihydroequilin analogously to the transformation of estrone into estradiol.[1] However, whereas the balance of mutual interconversion of estrone and estradiol is largely shifted in the direction of estrone, it is nearly equal in the case of equilin and 17β-dihydroequilin.[1] As such, although 17β-dihydroequilin is only a minor constituent of CEEs, it is, along with estradiol, the most important estrogen relevant to the estrogenic activity of the medication.[1]

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Pharmacokinetics

17β-Dihydroequilin has about 30% of the relative binding affinity of testosterone for sex hormone-binding globulin (SHBG), relative to 50% for estradiol.[1] The metabolic clearance rate of 17β-dihydroequilin is 1,250 L/day/m2, relative to 580 L/day/m2 for estradiol.[1]

Chemistry

See also: List of estrogens § Equine estrogens

17β-Dihydroequilin, or simply β-dihydroequilin, also known as δ7-17β-estradiol or as 7-dehydro-17β-estradiol, as well as estra-1,3,5(10),7-tetraen-3,17β-diol, is a naturally occurring estrane steroid and an analogue of estradiol.[1] In terms of chemical structure and pharmacology, equilin (δ7-estrone) is to 17β-dihydroequilin as estrone is to estradiol.[1]

References

  1. [1]
    Kuhl H (2005). "Pharmacology of estrogens and progestogens: influence of different routes of administration" (PDF). Climacteric. 8 (Suppl 1): 3–63. doi:10.1080/13697130500148875. PMID 16112947. S2CID 24616324.
  2. [2]
    Fritz MA, Speroff L (28 March 2012). "Postmenopausal Hormone Therapy". Clinical Gynecologic Endocrinology and Infertility. Lippincott Williams & Wilkins. pp. 751–. ISBN 978-1-4511-4847-3.
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