Inadequate levothyroxine replacement for primary hypothyroidism is associated with poor health-related quality of life–a Brazilian multicentre study

This study aimed to verify the impact of levothyroxine replacement on health-related quality of life (HRQoL) in a Brazilian sample of primary hypothyroidism patients. A cross-sectional study was performed with 2,057 consecutive primary hypothyroidism patients on levothyroxine (LT4) replacement at four referral centers in Brazil (median age = 53; 25th percentile = 43; 75th percentile = 61 years). Patient biochemical data were acquired from medical records, and patients completed a questionnaire on socioeconomic issues and clinical signs and symptoms of hypothyroidism. HRQoL was assessed using the SF-36v2. Patients were divided into three groups according to TSH levels: overtreated (OvT; TSH < 0.4 mU/L), appropriately treated (AT; TSH between 0.4 and 4.0 mU/L), and undertreated (UnT; TSH > 4.0 mU/L). Patients were also analyzed by TSH and FT4 serum levels: overt hyperthyroidism (OHyper; TSH < 0.4 mU/L and FT4 > 1.9 ng/dL), subclinical hyperthyroidism (SHyper; TSH < 0.4 mU/L and FT4 0.8–1.9 ng/dL), subclinical hypothyroidism (SHypo; TSH > 4.0 mU/L and FT4 0.8–1.9 ng/dL), and overt hypothyroidism (OHypo; TSH > 4.0 mU/L and FT4 < 0.8 ng/dL). A total of 14.4 % of patients were OvT, with 13.0 % SHyper and 1.4 % OHyper. The prevalence of UnT was 25.9 %, with 21.5 % SHypo and 4.4 % OHypo. Overtreatment was not associated with HRQoL impairment. UnT patients had worse HRQoL than AT patients, especially for physical and emotional aspects, independent of SHypo or OHypo status. Hypothyroidism undertreatment is associated with poor patient HRQoL. Therefore, adequate LT4 therapy should be given to maintain serum TSH within the reference range.