STUDIES OF SEXUAL DIFFERENTIATION OF SHEEP

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Abstract
Ewes [40] were given i.m. testosterone cypionate injections (200 mg) on each of the 20th, 27th and 40th days of gestation. This treatment ensured fetal exposure to testosterone from day 20 to day 65. Forty untreated ewes acted as controls. At birth, pre-natally androgenized male lambs were anatomically normal, but similarly treated female offspring displayed complete external genital masculinization including the presence of a prepuce, penis and scrotum and the absence of an external vulval opening. No male gonads were present. Internally, the female lambs possessed ovaries, uteri, cervices and vagina of normal appearance. Two-weekly blood plasma samples were withdrawn from 10 androgenized and 6 control female offspring and 8 androgenized and 8 control male offspring from 4-30 wk of age. Testosterone levels in males and LH [lutropin] levels in males and females were measured by radioimmunoassay. Analyses of variance showed that post-natal plasma LH levels in pre-natally androgenized lambs (male and female) were significantly depressed (P < 0.001), and that plasma testosterone concentrations in pre-natally androgenized males were subsequently depressed (P < 0.001). Pre-natal androgenization apparently impaired hypothalamic hypophysiotropic and/or pituitary function the 1st 30 wk of post-natal life which resulted either directly, or indirectly via reduced LH output, in a suppression of teste testosterone production.