DETERMINATION OF THE RATE OF TREATMENT WITH OVER OR UNDERDOSE OF PATIENTS UNDER LEVOTHYROXINE REPLACEMENT THERAPY

ABSTRACT

Purpose: Primary thyroid disease accounts for over 95 percent of cases of hypothyroidism. It is aimed that patients with primary hypothyroidism become euthyroid by reaching the target thyroid stimulating hormone (TSH) level with levothyroxine sodium (LT4) replacement therapy. In this study, it was aimed to evaluate the patients who could not be treated optimally and to determine the frequency of patients treated with overdose or underdose. 

Methods: This retrospective study was carried out on 500 patients diagnosed with primary hypothyroidism who were followed up at Necmettin Erbakan University Meram Faculty of Medicine hospital, are over 18 years of age, without thyroid malignancy, and who had been receiving fixed dose LT4 replacement therapy for the last 6 months between January 2015 and December 2016. Serum TSH, free triiodothyronine (fT3) and free thyroxine (fT4) levels were used to determine the thyroid hormone status of the patients. Body mass index (BMI) of all patients were evaluated. Low density lipoprotein (LDL), high density lipoprotein ( HDL), very low density lipoprotein (VLDL), triglyceride and total cholesterol data of the patients were included in the analysis. 

Results: TSH levels were not within the desired target range in 66.8% (n=334) of patients under LT4 replacement therapy. While TSH level was higher than the desired target range in 50.8% of the patients (treatment with underdose), 16.0% of the patients had TSH levels below the desired target range (treatment with overdose). Only 20.6% of the patients had normal body weight. The prevalence of dyslipidemia was 69.2% in men and 68.9% in women and there was no significant difference between the genders (p = 0.968). 

Conclusion: In our study, it was observed that most patients under LT4 replacement therapy were not in the desired TSH range. When serum TSH levels cannot be normalized with LT4 therapy, an interdisciplinary diagnostic approach and careful history should be taken. 

Key words: Primary hypothyroidism, Target TSH, Overdose, Underdose, Dyslipidemia