Effects of cold exposure on plasma growth hormone in the adrenalectomized and thyroparathyroidectomized rat

It has previously been shown that plasma radioimmunoassayable growth hormone (GH) falls following exposure to cold. This response was examined in the normal, adrenalectomized, thyroparathyroidectomized, and adrenalectomized-thyroparathyroid-ectomized rat to determine the effects of the absence of corticosterone (B) and of the thyroid and parathyroid glands on this response. GH decreased from a high prestress level to a low poststress level in both the normal and adrenalectomized animal. The thyropara-thyroidectomized and the adrenalectomized-thyroparathyroidectomized rats had a low prestress GH level, which was not decreased further following cold exposure. The prestress B levels were higher in the thyroparathyroidectomized animals than in the normal. Poststress levels of B were similar in both groups. It appears that an intact thyroid and/or parathyroid gland is necessary to maintain the normal resting plasma levels of GH and B, whereas stress levels do not appear to be affected.