RESUMO
The aim of this study was to determine circannual changes in the serum concentrations of thyroxine, calcitonin and parathormone in mature and immature red deer females. Blood samples from 8 hinds were collected monthly for 26 months. Secretions of thyroxine and calcitonin showed circannual rhythms with significantly higher levels in the immature hinds compared to the mature animals (p<0.05). For thyroxine, the concentration was higher in the winter/spring period than in summer/autumn (p<0.05), while for calcitonin the concentration profile was the opposite (p<0.05). The concentration of parathormone was significantly higher in summer/autumn that in the other months of the experiment (p<0.01). These results may indicate that the hormones investigated may be involved in the regulation of seasonal reproductive activity and in processes contributing to entering puberty in red deer females.
