Our aim was to evaluate the effects of iatrogenic, acute and deep hypothyroidism on nasal mucociliary clearance. A total of 46 patients undergoing total or near total thyroidectomy for differentiated thyroid cancer between March and June 2012, and scheduled to undergo radioactive iodine (I-131) ablation therapy followed with an induced hypothyroidism for routine screening were included in the study. Mucociliary clearance test was made during hypothyroid and euthyroid periods in all the patients included in the study. Of the 46 patients included in the study, 37 (%80.4) were females, 9 (%19.6) were males, and the average mucociliary clearance times were 16.78 and 9.58 min during hypothyroid and euthyroid periods, respectively. When the results were compared statistically, mucociliary clearance time measured during hypothyroidism period was found to be significantly longer than the one measured during euthyroid period. Mucociliary clearance time was found to be long during iatrogenic acute and deep hypothyroid periods. During these periods, patients should be followed closely for lower and upper respiratory tract infections.