Changes in the levels of growth hormone, insulin, somatomedin C and thyroxine in sheep during immunization against somatostatin.

The time-related changes in the plasma levels of growth hormone, insulin, somatomedin C and thyroxine following immunization against somatostatin, have been examined in sheep. In both the treated and control lambs there was a significant increase (P less than 0.01) in growth hormone levels with time from the start of the study (at three weeks of age) through until 13 weeks of age. This increase was mirrored by increasing somatomedin C (IGF-1) levels (P less than 0.001). Thyroxine levels did not change during the period of the study. Immunization against somatostatin did not produce any significant difference between treatment groups or between sexes in the levels of growth hormone or thyroxine. However, IGF-1 level were significantly increased (P less than 0.01) by the treatment in both sexes. The changes in the levels of insulin were complicated by a marked difference between the control groups; the control females being significantly different (P less than 0.001) from all the other animals.