Obesity, Thyroid and OSA: An Intriguing Triangle.

ABSTRACT

The complex relationship between BMI, thyroid and its effects on OSA raises a question on how patients with suspected OSA should be evaluated. Some studies have described an association between thyroid disorders and OSA. Whether this is a direct effect of thyroid disorders, or it is indirectly related to BMI values is an important point to ponder. The aim of this study was to estimate the prevalence of thyroid disorders in relation to BMI in newly diagnosed patients with OSA (AHI > 5/h on diagnostic Polysomnography) at sleep lab of our tertiary care centre. In addition, we compared baseline characteristics of OSA patients with thyroid parameters. MATERIAL: In this hospital based observational study, recently diagnosed OSA on the basis of PSG showing AHI > 5/ h according to the AASM 2012 scoring rules and age more than 18 years were recruited from OPD and in-patients of SMS Medical College Jaipur. Patients on previous CPAP treatment, mixed or predominantly central sleep apnea, known diabetics and language barriers or cognitive or psychiatric disorders that made informed consent difficult to obtain were excluded. OBSERVATION During the study period, 65 patients with treatment naïve OSA and a mean age of 52.28±10.92 year, a mean body mass index (BMI) of 34.73±7.20 kg/m2 underwent thyroid function tests. In the OSA patients, the prevalence of newly diagnosed clinical hypothyroidism was 12.3%. In Mild OSA the mean FT3 (ng/ml), FT4 (ng/dl), TSH (mIU/l) and mean AHI score was 3.10±0.71, 1.37±0.58, 3.64±1.37 and 7.74±3.55 respectively. Similarly, mean FT3 (ng/ml), FT4 (ng/dl), TSH (mIU/l) and mean AHI score were 2.97±0.93, 1.46±0.79, 6.33±8.05 and 17.42±88.90 respectively in moderate OSA and 3.32±0.58, 1.23±0.46, 3.55±1.82 and 45.54±21.38 respectively in severe OSA. There was a statistically significant difference between mild moderate and severe OSA regarding thyroid profile as well as BMI with p of <0.05. CONCLUSION: The prevalence of hypothyroidism was common among patients with OSA and the severity of OSA correlated with thyroid function tests and BMI.