The effects of obesity on thyroid function have not been well established. The aim of this study was to investigate the effects of body mass index (BMI) and/or non-alcoholic fatty liver disease (NAFLD) on thyroid function.

A retrospective longitudinal analysis was conducted among subjects who underwent comprehensive health check-ups at least four times between 2008 and 2017. Thyroid function was investigated according to BMI or presence of NAFLD at the end of follow-up. The subjects were divided into four groups: control (n = 216), subjects with obese (n = 94), subjects with NAFLD (n = 48), and subjects with obese + NAFLD (n = 93). Obesity was defined as BMI ≥ 25 kg/m².

During the mean follow-up of 6.8 years (6.8 ± 1.2 years), 42 of the 451 subjects (9.3%) had subclinical hypothyroidism (SCH) but no subjects developed overt hypothyroidism. In multivariate Cox proportional hazard analysis, after adjustment for age, sex, smoking, and baseline thyroid stimulating hormone level, obese subjects with NAFLD had a higher risk of SCH than the control group.

The obese subjects with NAFLD had a higher risk for SCH in the future.

To evaluate the efficacy and predictive factors of Dipeptidyl peptidase-4 (DPP-4) inhibitors in type 2 diabetes mellitus (T2DM) patients who were not well controlled with other oral antidiabetic drugs or insulin in real clinical practice.

From December 2012 to January 2014, retrospective longitudinal observation study was conducted for patients with T2DM who were not reached a glycemic target (glycated hemoglobin [HbA1c] > 6.5%) with other oral antidiabetic drugs or insulins. Type 1 diabetes or other types of diabetes were excluded. Responders were eligible with decreased HbA1c from baseline for more than 5% during follow up period.

Of total 135 T2DM patients having an average 9.0 months follow-up period, 84 (62.2%) of patients were responder to DPP-4 inhibitors. After concomitant treatment with DPP-4 inhibitors, patients had a mean decrease in HbA1c of 0.69 ± 1.3%, fasting plasma glucose of 13 ± 52 ㎎/㎗, and postprandial plasma glucose of 29 ± 85 ㎎/㎗ from baseline (all P< 0.05). Independent predictive factor for an improvement of glycemic control with DPP-4 inhibitors was higher baseline HbA1c (odds ratio 2.07 with 95% confidence interval 1.15–3.72) compared with non-responders.

A clinical meaningful improvement in glycemic control was seen when DPP-4 inhibitors were added to other anti-diabetic medications in patients with T2DM regardless of age, duration of T2DM, type of combination treatment regimen. Patients who had higher HbA1c were more easily respond to DPP-4 inhibitors treatment in short-term follow-up period.

We conducted a study to investigate the normal range for TSH and within-individual variations of TSH according to temperat䴸re and aging.

We enrolled patients who underwent periodic medical examinations five times over a six year period (2007.8~2013.6). Anthropometric data and thyroid ultrasonography were evaluated, and serum TSH, T3, and T4 were assayed.

Subjects were 19-64 years old, 120 were female, and 208 were male. Reference ranges for TSH were 0.53-4.94 mlU/L in the first test, 0.49-5.61 mlU/L in the second test, 0.46-6.06 mlU/L in the third test, 0.48-5.99 mlU/L in the fourth test, and 0.52-6.3 mlU/L in the fifth test. When the TSH level was analyzed according to temperature and sex, mean TSH was higher in months in which the average monthly temperatures were below 10⁰C in Jinju, Gyeongnam and female. The aging and low temperatures are associated with increased serum TSH concentrations in the within-individual.

This study showed that aging is associated with increased serum TSH concentrations in the within- individual and serum TSH concentrations are different in the within-individual according to the temperature.