Background: Thyroxine (T4) and triiodothyronine are the main thyroid hormones that play an essential role in cellular metabolism, growth, and tissue development, and subclinical hypothyroidism (SCH) is often defined by a thyroid-stimulating hormone (TSH) level above the upper limit of the reference range (usually around 4.0 or 4.5 mIU/L, usually TSH level in between 4 and 10 mIU/mL) along with a normal free T4 (fT4) level. Previous studies undertaken in various parts of the world have shown food intake can influence the TSH level at different percentages and these studies speculated that if we measure TSH level 2 h after breakfast (9:00 am) compared with the fasting blood samples that is generally collected in the morning (7:00 am), the TSH level is significantly reduced by about 30%, and this significant difference created reasonable doubt in the diagnosis of SCH.
Aims and Objectives: The study aimed to evaluate the difference in serum TSH, fT4, leptin, cortisol, insulin, adiponectin, and glucagon-like peptide-1 (GLP-1) between fasting and post-prandial blood samples in known subclinical hypothyroid patients.
Materials and Methods: This descriptive, cross-sectional, non-interventional study was done on 50 diagnosed subclinical hypothyroid patients after screening them through the inclusion–exclusion criteria. The estimations were done by chemiluminescence immunoassay or enzyme-linked immunosorbent assay method, statistical analysis was done using Statistical Packages for the Social Sciences.
Results: After analysis of blood samples, it showed that the serum TSH decreased progressively after food intake for almost 2 h, the level of decrease is statistically significant (from 7.38 ± 1.22 mIU/mL to 5.9 ± 1.03 mIU/mL) (P < 0.001). Serum fT4 level remained almost unchanged after food intake.
Conclusion: As per previous and our study a possible explanation of this post-prandial fall of TSH can be that food consumption causes an alteration in circulating glucose levels, insulin, leptin, gastric inhibitory polypeptide (cholecystokinin and GLP-1), and cortisol. Growth hormone (GH) and somatostatin levels also suppress TSH secretion from the pituitary. As both over- and under-treatment with eltroxin can be detrimental for subclinical hypothyroid children and pregnant women, so further studies with larger sample sizes and somatostatin and GH estimation should be done to authenticate the findings of this study.
Key words: Thyroid Function Test; Fasting; Post-Prandial; Subclinical Hypothyroid Patient
|
