J. Inoue et al., SERUM LEVELS OF TESTOSTERONE AND ESTROGENS IN NORMAL AND INFERTILE STALLIONS, International journal of andrology, 16(2), 1993, pp. 155-158
The serum concentrations of testosterone and oestrogens were determine
d in stallions classified as geldings, normal (according to age) or in
fertile (azoospermic). There were significant differences in testoster
one and oestrogen levels between the groups. Normal concentrations of
testosterone and total oestrogens were attained after 16 months of age
. Castrated and immature horses (< 15 months of age) had lower levels
of testosterone and total oestrogens than did mature and infertile sta
llions. Azoospermic stallions had lower levels of testosterone and tot
al oestrogens than did normal mature horses except in one case (B4) in
which the level of total oestrogens was increased markedly. Critical
ellipses for testosterone and total oestrogens were obtained for both
groups (6- 15-month-old colts and stallions aged > 4 years). The resul
ts suggest that serum levels of testosterone and total oestrogens may
provide a sensitive index of the endocrine function of the testis in m
ale horses.