Endocrine Abstracts

Hypothyroidism is associated with modest weight gain, but there is a lack of clarity regarding subclinical hypothyroidism and obesity. Studies with bariatric surgery showed that 15–25% of extremely obese subjects had subclinical hypothyroidism. Therefore the goal of this study was to evaluate the effect of intensified life style intervention on insulin sensitivity, irisin concentration and thyroid function parameters.

Methods: A randomized interventional clinical study (NCT02325804) included life style intervention: hypocaloric diet (30% restriction of calories) and physical activity 150 minutes/week. Before and after 8 weeks of intervention all patients underwent complete medical examination (measurement of physical fitness, resting metabolic rate (RMR), body composition analysis, oral glucose tolerance test, parameters of lipid metabolism, irisin concentration and thyroid function parameters. Insulin sensitivity was evaluated according to the homeostasis model assessment of insulin resistance (HOMA-IR) and insulin sensitivity indices according Matsuda and Cederholm were calculated (ISIMat and ISICed).

Results: So far 43 patients (14 M/29 F, mean age 43±12 yrs., body fat % 36±6) finished the intervention. At baseline 9 patients had thyroid stimulating hormone (TSH) in the range 2.5–5.0 ng/ml, indicating subclinical hypothyroidism. The average reduction of body weight was 6.8±4.9 kg (0–15 kg; P≤0.0001), Insulin sensitivity improved (IR HOMA 2.71±3.90 vs. 1.24±0.83; P=0.01; ISIMat 6.64±4.38 vs. 8.93±5.36 P≤0.001; ISICed 59.1±21.4 vs. 64.7±22.2 P=0.03). TSH significantly decreased after intervention (2.04±1.24 vs. 1.69±0.81 P=0.03) and free thyroxine remained unchanged (13.7±2.7 vs. 13.4±2.9, P=0.7). Plasma irisin significantly decreased after intervention (233±66 vs. 167±88 ng/ml; P≤0.001) and positively correlated with ISImat, however only after intervention (P 0.05).

Conclusion: Results of our study are in line of previous results about beneficial effect of intensive life style changes on insulin sensitivity and thyroid function. Novel view indicates that changes in thyroid-stimulating hormone (TSH) could well be secondary to obesity. Supported by grants APVV 15-0228; VEGA 2/0161/16