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<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<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<0.05), and the physiological increase in glucagon after protein ingestion (p<0.05) was not associated with any changes in TT₄, FT₄, TT₃, FT₃, or rT₃ that could indicate changes in the 5′-deiodinase activity.

Key Words:

• 5′-deiodination
• Food
• Regulation
• Metabolism
• Nutrition
• pituitary hormones
• thyroxine
• triiodothyronine