A comparative study on outcomes of preprandial versus postprandial thyroid function test

Abstract

Background: The thyroid is an endocrine gland. It secretes two hormones thyroxine (T 4), triiodothyronine (T 3). Hypothyroidism is a common condition encountered by a clinician. Subclinical hypothyroidism (SCH) defined as normal free thyroxine (T4) and elevated thyroid stimulating hormone (TSH), is primarily a biochemical diagnosis with or without clinical symptoms. Studies have observed that TSH levels vary at different times in a day. In practice not much importance is given to the timing of the sample collection (pre-prandial or post-prandial sate). SCH is diagnosed depending on TSH value. So the condition may be under or over diagnosed based on a single value. So we conducted this study to determine whether timing of sample collection had any significant relationship in the determination of levels of thyroid hormones. Methods: The study was carried on 114 patients who visited ENT department, NMCH between July 2018 and June 2019. Group-1 consisted of 38 normal patients. Group-2 consisted of 36 hypothyroidism patients GROUP-3 consisted of 40 subclinical hypothyroidism patients. Thyroid function tests (TSH and free T4) were done in fasting state and 2 hours postprandially. Results: TSH values were found to be significantly lowered after food in all the three groups. Free T4 values did not show any statistically significant alteration after food. Conclusions: There was a significant decline in TSH values postprandially. This might lead to inappropriate diagnosis and management of patients as cases of hypothyroidism, especially in cases of sub clinical hypothyroidism.