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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| Other names | β-Dihydroequilin; Δ7-17β-Estradiol; 7-Dehydro-17β-estradiol; Estra-1,3,5(10),7-tetraen-3,17β-diol; NSC-12170 |
| Routes of administration | By mouth |
| Drug class | Estrogen |
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| ECHA InfoCard | 100.020.576 |
| Chemical and physical data | |
| Formula | C18H22O2 |
| Molar mass | 270.372 g·mol−1 |
| 3D model (JSmol) | |
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Pharmacology
editPharmacodynamics
edit17β-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]
| Estrogen | HF | VE | UCa | FSH | LH | HDL-C | SHBG | CBG | AGT | Liver |
|---|---|---|---|---|---|---|---|---|---|---|
| Estradiol | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 |
| Estrone | ? | ? | ? | 0.3 | 0.3 | ? | ? | ? | ? | ? |
| Estriol | 0.3 | 0.3 | 0.1 | 0.3 | 0.3 | 0.2 | ? | ? | ? | 0.67 |
| Estrone sulfate | ? | 0.9 | 0.9 | 0.8–0.9 | 0.9 | 0.5 | 0.9 | 0.5–0.7 | 1.4–1.5 | 0.56–1.7 |
| Conjugated estrogens | 1.2 | 1.5 | 2.0 | 1.1–1.3 | 1.0 | 1.5 | 3.0–3.2 | 1.3–1.5 | 5.0 | 1.3–4.5 |
| Equilin sulfate | ? | ? | 1.0 | ? | ? | 6.0 | 7.5 | 6.0 | 7.5 | ? |
| Ethinylestradiol | 120 | 150 | 400 | 60–150 | 100 | 400 | 500–600 | 500–600 | 350 | 2.9–5.0 |
| Diethylstilbestrol | ? | ? | ? | 2.9–3.4 | ? | ? | 26–28 | 25–37 | 20 | 5.7–7.5 |
Sources and footnotes
Notes: Values are ratios, with estradiol as standard (i.e., 1.0). Abbreviations: HF = Clinical relief of hot flashes. VE = Increased proliferation of vaginal epithelium. UCa = Decrease in UCa. FSH = Suppression of FSH levels. LH = Suppression of LH levels. HDL-C, SHBG, CBG, and AGT = Increase in the serum levels of these liver proteins. Liver = Ratio of liver estrogenic effects to general/systemic estrogenic effects (hot flashes/gonadotropins). Sources: See template. | ||||||||||
Pharmacokinetics
edit17β-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
edit17β-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
edit- ^ a b c d e f g h i j k l m n o 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.
- ^ 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.