<prompt> The best marker for hypehyroidism -T3T4TSHThyroglobulin  <response>: The thyroid-stimulating hormone TSH assay is the most reliable test for diagnosing primary hypo- and hypehyroidismTSH secretion is pulsatile and follows a circadian rhythm. Major secretory pulses occur between 10 p.m. and 4 a.m., and the mean levels are approximately 1.3-1.4 mIUL, with a lower limit of 0.3-0.5 mIUL and an upper limit of 3.9-5.5 mIUL 10Changes in serum TSH levels can be attributed to its pulsatile and nocturnal secretion Currently, the normal reference range of serum TSH for adults is 0.4-4.5 mIUL . Consistent studies confirm that serum TSH levels are age-dependent and that adult reference values do not correspond to those observed in pediatric patients; TSH levels continuously decrease from the neonatal period until the end of adolescence . Ref - pubmed.com 