Different short-term effect of protein and carbohydrate intake on TSH, growth hormone (GH), insulin, C-peptide, and glucagon in humans

Abstract

The effect of isocaloric (500 kcal) protein and carbohydrate ingestion was studied in a crossover study in nine healthy humans. Subjects were studied twice after overnight fasting, with an interval of 3 to 7 days. Blood was collected for 240 min after food ingestion. The initial reaction of growth hormone (GH) and thyroid stimulating hormone (TSH) to protein and carbohydrate was identical, with a reduction in both GH and TSH, and nadir occurring after 45-60 min and 120 min, respectively. During the next 120 min TSH returned to starting level after carbohydrate intake but was still reduced after protein intake (p less than 0.04). After both diets GH increased after the initial decline, the increase was greatest after protein intake and maximum was reached at 180 min (p less than 0.02). It has been reported that the 5'-deiodination of T4 is stimulated by insulin and inhibited by glucagon. The physiological increase in insulin after carbohydrate ingestion (p less than 0.05), and the physiological increase in glucagon after protein ingestion (p less than 0.05) was not associated with any changes in TT4, FT4, TT3, FT3, or rT3 that could indicate changes in the 5'-deiodinase activity.