Age dependent changes in plasma anti-Mullerian hormone concentration in the bovine male, female and freemartin from birth to puberty: relationship with testosterone production and influence on sex differentiation

To understand the behaviour of the gonads, in terms of hormonal secretion, in a model of intersexual development naturally occurring in mammals, we determined plasma concentrations of testosterone, progesterone, and anti-M€ullerian hormone (AMH) in bovine freemartins, and compared them to normal levels measured in males and females from birth to puberty. We found that newborn males and freemartins have very high concentrations of AMH (over 700 ng/ml). Conversely, plasma AMH concentration is always below 120 ng/ml in females. While values remain stable in males for the first five months of life, they sharply decrease in the freemartins within the first fortnight, and reach female levels, which demonstrates that AMH is essentially originated in the male twin. In young bulls the trend of plasma testosterone concentrations is opposite to that of the AMH. The rise in testosterone production at puberty corresponds to a sharp decline in AMH concentrations. Bovine plasma concentrations of AMH are surprisingly higher than those measured in other mammals, including man and mouse. The results obtained are discussed in reference to comparative aspects of endocrine functions.