TSH level decrease at 2 h after food intake might affect subclinical hypothyroidism diagnosis

China: The thyroid stimulating hormone (TSH) level at 2 h after the food intake decreased significantly by about 30% compared with the fasting state which in turn might influence th diagnosis of subclinical hypothyroidism, states a recent study. The study was published in the journal BMC Endocrine Disorders on 01 April 2022. 

Previous studies have shown that TSH secretion and its blood level exhibit a circadian rhythm due to which it becomes necessary to further investigate the difference blood TSH concentration between 7:00 am and 9:00 am after meal to determine if it is affected by the food intake or diurnal rhythm. Therefore, Aimei Dong, Department of Endocrinology, Peking University First Hospital, Beijing, China, and colleagues aimed to investigate the effects of blood sampling after calorie intake on TSH level, compared with blood sampling in fasting state in a prospective, randomized, controlled study. 

The study included subjects from the outpatients in the department of endocrinology without evidence of thyroid diseases. They were then randomiaed into the fasting group, diet intake group, and glucose intake group, respectively. Collection of fasting blood was done from all subjects at 7:00 am for the measurement of TSH and free thyroxine (FT4) concentrations. Following which, the participants were maintained at fasting state (fasting group), had an intake of the mixed diet with 400 kcal calories (diet intake group), and had an intake of 75 g glucose (glucose intake group), respectively. The blood was collected again 2 h later (9:00 am on the same day) for TSH and FT4 level measurement and comparison. 

The study enrolled a total of 150 subjects, out of which 146 met the inclusion criteria, with 48, 48, and 50 in the diet intake group, glucose intake group, and fasting group, respectively.