Oestrone Sulphate

Can be used as a test for cryptorchidism although anti-mullerian hormone is
preferred.

Mainly used as a pregnancy test. Non-pregnant mares typically show values
<10 ng/mL. Produced by foetal gonads and crosses placenta into the maternal
circulation so also confirms foetal viability when high. Concentrations change
through pregnancy and exhibit considerable individual variability meaning
borderline values should be rechecked.

Best used between 4 months and 9 months, with peak values around 5-6
months. Falls toward the end of pregnancy but rarely low enough to return
false negative results at this time.

Oestrone sulphate concentration during mare pregnancies showing mean values (central
black line) and minimum and maximum values (grey area).