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Clinical Endocrinology of Pregnant Mares
Published in Juan Carlos Gardón, Katy Satué, Biotechnologies Applied to Animal Reproduction, 2020
In late gestation, total estrogen levels (including E1S, E2 and its metabolites, equilin, and equilenin) as well may be used for fetal and placental health monitoring. Although total estrogen concentration >1000 ng/mL between 150 and 280 days of gestation is considered to be normal, values <500 ng/mL have been associated with a severely compromised or death fetus and between 500 and 800 ng/mL indicate stress or fetal weakness. However, it is doubtful that total estrogen concentration can predict fetal death as the fetal gonads are unlikely to respond to fetal stress (Bucca, 2006; LeBlanc, 2010; Shikichi et al. 2017).
Alternate Pathways of Steroid Biosynthesis and the Origin, Metabolism, and Biological Effects of Ring B Unsaturated Estrogens
Published in Ronald Hobkirk, Steroid Biochemistry, 1979
B. R. Bhavnani, C. A. Woolever
Animal and human tests of the estrogenic potency of equilin, equilenin, and their 17-reduced derivatives center mainly about their ability to stimulate growth in the tissues of the female reproductive tract. Equilin and 17β-dihydroequilin are seen to be potent estrogens while equilenin and its 17β-reduced derivatives and the 17α-reduced derivatives of both have been shown to have little or no effect in the tests used. The metabolic effects of the ring B unsaturated compounds have not yet been investigated individually but only as components of the conjugated equine estrogen preparations.
Primary choice of estrogen and progestogen as components for HRT: a clinical pharmacological view
Published in Climacteric, 2022
Remarkably, the content of 17β-estradiol is only about 1%. It is produced by the metabolism of estrone, the amount of which, however, is dependent on the activity of 17β-reductases differing in the target tissues such as the brain, bone, urogenital tract and vasculature. Likewise, other components can also function as prodrugs for active metabolites. Equilin can be metabolized to 17β-dihydroequilin (and vice versa) or to equilenin [13], both with strong biological activities, as presented in Table 4 [14]. This table summarizes several experimental studies in ovariectomized rats, showing the mean percentages of the CEE components used in these studies and the biological activity with respect to the potency in the vagina and uterus. The strong efficacy of these equine estrogens has been also shown in a variety of clinical studies with different results according to different endpoints. For example, equilenin increased the hepatic proteins high density lipoprotein-cholesterol, SHBG, CBG and angiotensinogen to a six or seven-times higher extent than the use of 17β-estradiol [14]. These effects are not dependent on the binding affinity to these proteins, which is about 30% lower for equilenin compared to 17β-estradiol [14].