Plasma concentrations of retinol, triiodothyronine, thyroxine, and iron were measured in captive adult California sea lions, as well as premature and full term free-living California sea lion pups and their mothers.

Plasma retinol concentrations were significantly lower (P = 0.0006) in premature pups than full term pups. In the same fashion, the mothers of the premature pups had significantly lower retinol concentrations than the mothers of the full term pups. Plasma iron concentrations of the premature pups were significantly higher (P < 0.05) than any of other groups of sea lions, and the captive adult sea lions had higher plasma iron than the wild adult sea lions. Differences in plasma triiodothyronine or thyroxin concentrations were not detected between these groups of sea lions.

Retinol, triiodothyronine, thyroxine, and iron are important indicators of heath and should be included in all medical evaluation of captive as well as free ranging marine mammals.