Does Acquired Hypothyroidism Affect the Hearing Functions?

Abstract

Purpose: It is well known that congenital hypothyroidism can cause hearing loss. However, conflicting results were found in studies investigating hearing functions in acquired hypothyroidism. Therefore, we evaluated the audiometric findings in patients with acquired hypothyroidism. Material and Method: The study included 58 patients with hypothyroidism and age- and gender-matched 34 healthy controls. Twenty eight (48.27%) patients had subclinical hypothyroidism, and 30 (51.73%) had obvious hypothyroidism. All subjects had a normal otoscopic examination and tympanometry. Pure tone audiometry at 250, 500, 1000, 2000, 4000, 6000, and 8000 Hertz (Hz) was performed in both groups. Blood pressure measurements and the levels of plasma electrolytes, lipids and vitamin B12 were available in all subjects. Results: Hypothyroidism group and control group were similar with respect to systolic and diastolic blood pressures and plasma glucose, lipid, vitamin B12, calcium, sodium, potassium, and chloride levels. Significantly higher audiometric thresholds (dB) at 250 (10 (0-45) vs. 5 (0-15), p<0.001) and 500 Hz (10 (0-40) vs. 10 (-5-15), p=0.003) were recorded in hypothyroid patients compared to that in healthy controls. Hearing thresholds at 250 and 500 Hz correlated positively with thyroid-stimulating hormone (TSH), and negatively with free triiodothyronine and free thyroxine. Subclinical hypothyroid patients had a higher hearing threshold at 250 Hz than healthy controls (p=0.001). Discussion: Our study demonstrated that hearing ability decreases in hypothyroidism, even in subclinical hypothyroidism. The changes in TSH and thyroid hormone levels seem to be directly related to the hearing loss in this population of patients.