Effects of diet composition on serum levels of insulin, thyroxine, triiodothyronine, growth hormone, and corticosterone in rats.

These studies were designed to determine the effects of diet composition on serum insulin, triiodothyronine, thyroxine, growth hormone, and corticosterone and to correlate these hormones with feed intake, body weight, and adipose tissue weight in rats. Experimental diets were fed for a period of 4 weeks. The experimental dietary groups were as follows: high starch (HST), high glucose (HG), high sucrose (HSU), high protein (HP), high saturated fat (HFS), and higher unsaturated fat (HFU). Serum glucose concentrations were not significantly different among any of the groups. The HST, HSU and HG diets produced the highest serum insulin. Serum thyroid hormone levels were highest in rats fed high fat diets. No significant differences in serum growth hormone or corticosterone levels were noted among the dietary groups. There was a tendency for rats fed a high protein diet to have higher concentration of corticosterone. However, there were no significant differences detected. There was a significant negative correlation between serum corticosterone and ovarian adipose tissue weight. It is concluded from these studies that these types of dietary manipulation have a significant effect on endocrine status and body fat deposition.