Seasonal changes in weight gain, growth hormone, and thyroid hormones in intact and castrated male moose (Alces alces alces)

Abstract

To elucidate possible endocrine mechanisms in the control of cyclic weight gain in moose, serum concentrations of growth hormone (GH), thyroxine (T4), and triiodothyronine (T3) were recorded during the year in two intact and one castrated male moose. Changes in the levels of these hormones were compared with changes in weight gain. Growth hormone often increased to peak values in April or May, but was generally low throughout the period of greatest weight gain. Thyroid hormone levels increased in spring and decreased in autumn, corresponding to onset and cessation of rapid weight gain. Changes in triiodothyronine levels may have been secondary to changes in food intake.