Steroid hormones and prolactin in the white whale (Delphinapterus leucas) of West Greenland

Abstract

Testosterone, progesterone, oestrogen and prolactin concentrations were determined in serum and urine samples collected from white whales (Delphinapterus leucas) taken by Greenlanders in the autumn of 1989-1991 and during May 1992. Hormone levels following long vs short intervals between hunting and isolation of serum samples were compared, and a significant difference was seen in the oestrogen concentrations.

In male white whales the testosterone levels were significantly higher in sexually mature animals as compared to immature animals, 4.14 vs 0.96 nmol/l in serum samples and 0.62 vs 0.11 creatinine index in urine samples, respectively.

Hormone levels of immature, pregnant, lactating and resting female white whales were compared, and the pregnant animals had higher levels of progesterone than the nonpregnant animals, 29.1 vs 1.76 nmol/l in blood and 22.1 vs 0.54 creatinine index in urine, respectively. The oestrogen level was higher in urine from pregnant females, 2.43 vs 0.37 creatinine index, but concentrations in serum were not significantly elevated. Lactating females had higher serum prolactin concentrations than nonlactating females, 4.35 vs 1.97 μg/l, respectively.