Endocrine changes and their relationship with body weight in growing yaks

The concentrations of growth hormone (GH), insulin (Ins), tri-iodothyronine (T3) and thyroxine (T4) in blood samples of growing yaks during different bimonthly seasons were determined by radioimmunoassay. The changes of body weight of growing yaks and composition of grass grazed were measured accordingly. The seasonal changes of hormones were significant (P