Demographic and Clinical Characteristics of Patients with Primary Hypothyroidism and Adequacy of Levothyroxine Replacement Therapy in Them: A Nationwide Study in Bangladesh

A BSTRACT Background: Despite the huge burden of primary hypothyroidism in Bangladesh, no nationwide study has been conducted describing the demographic and clinical characteristics of these patients; data on the adequacy of levothyroxine (L-T4) replacement are also lacking. This study aimed to fill the knowledge gap. Materials and Methods: This cross-sectional study was conducted among patients with primary hypothyroidism attending the endocrinology outpatient clinics of several hospitals throughout Bangladesh from July 2023 to December 2023. Adults with primary hypothyroidism who had been on L-T4 replacement for at least 1 year were included. Data on their demographic and disease-related characteristics were collected. Serum thyroid-stimulating hormone (TSH) was measured; TSH 0.4–4.0 μIU/mL was considered the therapeutic target for nonmalignant thyroid cases. Results: Two thousand six hundred and forty-one patients (median age 37 years, 86.4% female, and median disease duration 5 years) were included. Hashimoto’s thyroiditis was the most common (40.9%) cause of hypothyroidism; 1.9% had differentiated thyroid cancer (DTC), and the etiology was not established in many (40.2%). Only 26.8% of patients had high adherence to L-T4. Among the non-DTC cases ( n = 2590), over half (53.9%) had TSH within the target range, whether the disease was uncontrolled in the remaining 46.1% (TSH was below the target range in 5.6% and above the target range in 40.5%). Among the DTC cases ( n = 51), only a few (9.8%) had a TSH within the target range; TSH was below and above the range in 2% and 88.2% of these patients, respectively. In the nonmalignant hypothyroid cases, vegetarian diet, smokeless tobacco use, disease duration >5 years, iron or calcium supplements consumption within 4 h of L-T4 intake, and low or medium adherence to L-T4 were associated with uncontrolled hypothyroidism. Conclusion: For nearly half of Bangladeshi patients with primary hypothyroidism, L-T4 replacement is not optimal. Physicians should address the barriers to reaching the therapeutic goal for these patients.