Gonadal function was evaluated in 100 home-reared persons with Down syndrome (DS) including 53 boys and men and 47 girls and women. In order to definitively evaluate gonadal function in our subjects, all patients with abnormal thyroid function were excluded from endocrine analysis. Among the men, the frequency of hypospadias and cryptorchidism was similar to that of the general population. In both men and women, the ages for the onset and completion of puberty were also normal. However, among adult men with DS, the mean stretched penile length and the mean testicular volume were significantly below the mean values of normal men. In the 23 men with DS, the mean serum levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were significantly elevated above the mean for normal men. By contrast, the mean plasma level of testosterone (T) was normal, suggesting a diagnosis of partial gonadal deficiency. Among the 14 women in this study, 6 had primary gonadal dysfunction. In prepubertal children, serum FSH levels in 3 boys and 5 girls were more than 2 SD above the mean for normal children, while serum levels of LH in 3 boys and 2 girls were abnormally elevated. When gonadal function was evaluated in male infants, serum levels of FSH were above the normal in 6 of 11 subjects. Serum LH was abnormally elevated in 3 of 8 female infants. Our data argue that primary gonadal deficiency is common in DS, that it is progressive from birth to adolescence, and that it is clearly manifest in adult patients.
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