Blood concentrations of gonadotrophins, prolactin and gonadal steroids in males and in non-pregnant and pregnant female African elephants ( Loxodonta africana )

No seasonal variation in any of the hormones measured was apparent in males or females. Testosterone levels in males increased around puberty (10-11 years) and remained significantly higher in adult than prepubertal males. This was not accompanied by any significant change in levels of LH, FSH or prolactin. In non-pregnant females there was no apparent difference in levels of LH, FSH or prolactin with age. There was a significant increase in progesterone around puberty (12 years) but there was considerable overlap in values between prepubertal and adult females. During pregnancy, progesterone levels were significantly higher than in non-pregnant females with maximum levels occurring at mid-pregnancy (9-12 months). However, there was considerable overlap in values between non-pregnancy and pregnancy. Concentrations of LH and FSH decreased significantly during mid-pregnancy while prolactin levels increased dramatically during pregnancy; after 7 months of gestation until term levels were always at least 8 ng/ml greater than in any non-pregnant female. It is suggested that this consistent increase in plasma/serum levels of prolactin can be used to diagnose pregnancy in the elephant.