Primary hypothyroidism in the community: Lower daily dosages of levothyroxine replacement therapy for Asian patients

Optimal levothyroxine dose to achieve euthyroidism in patients with primary hypothyroidism: analysis according to etiology

INTRODUCTION

Levothyroxine (LT4) has been considered the standard of care for treatment of hypothyroidism. Current recommendations suggest a LT4 dose between 1.6-1.8 µg/kg/day. The aim of this study was to evaluate the LT4 dose for adult patients with primary hypothyroidism of different etiologies who reached euthyroidism.

METHODS

A cross-sectional study was performed from the retrospective review of the charts of patients with primary hypothyroidism in treatment with LT4. Subjects were classified according to TSH level in overtreated (TSH < 0.4 µIU/ml), euthyroid (TSH 0.40-4.20), and undertreated (TSH >4.2) and according to the etiology of hypothyroidism. A stepwise logistic regression model was performed to evaluate the variables associated with TSH<0.4 µIU/ml.

RESULTS

955 patients were included. 75.13% of the patients had an adequate LT4 replacement. LT4 dose to achieve euthyroidism was higher in patients with a history of radioiodine therapy (1.92 μg/kg) and thyroid surgery (1.52 μg/kg), while the LT4 dose required to achieve euthyroidism in patients with Hashimoto's thyroiditis and atrophic thyroiditis was lower than that reported in previous studies (1.25 and 1.08 μg/kg, respectively). The variables that were associated with a higher probability of TSH<0.4 µIU/ml were male gender, Hashimoto's thyroiditis, radioiodine therapy, and thyroid surgery.

MAJOR CONCLUSION

LT4 dose required to achieve euthyroidism in patients with hypothyroidism varies according to the etiology, being higher in patients with hypothyroidism due to radioiodine therapy and thyroid surgery. Patients with hypothyroidism due to Hashimoto's thyroiditis and atrophic thyroiditis require a lower dose than current recommendations.

Appropriate dose of levothyroxine replacement therapy for hypothyroid obese patients

Background

Athyreotic patients require a daily levothyroxine (LT4) doses of 1.6-1.8 mcg/kg of actual body weight (BW) to achieve normal thyroid stimulating hormone (TSH) levels. Lean body mass (LBM) calculation may be a more accurate determination of LT4 dose in obese patients. Previous studies were mainly investigated in Caucasians and LBM is markedly different between various ethnic groups. We aim to identify the optimal dose of LT4 replacement therapy in hypothyroid Thai patients including obese subjects.

Methods

We retrospectively reviewed the medical records of Thai adults with hypothyroidism at the thyroid clinic. Patients had been received LT4 (Brand: Euthyrox) at a stable dose ≥ 75 mcg/day for at least 1 year. Patients with thyroid cancer, pregnant, and lactating women were excluded. LBM was calculated by the Hume formula.

Results

Two hundred patients (80% females) with a mean age of 48.6 ± 14.8 years and a body mass index (BMI) of 24.5 ± 4.6 kg/m² were included. Daily LT4 dose/kg of actual BW according to BMI 18.5-24.9, 25-29.9, and ≥ 30 kg/m² were 1.67 ± 0.27, 1.51 ± 0.28 and 1.39 ± 0.34 mcg/kg, respectively. In contrast, LT4 dose/kg of LBM were 2.31 ± 0.39, 2.35 ± 0.45 and 2.36 ± 0.51 mcg/kg, respectively.

Conclusions

LBM is considered a better indicator for calculating an appropriate LT4 replacement dose than actual BW in hypothyroid obese Thai patients. The recommended daily dose of LT4 is 2.3 mcg/kg of LBM that could be applied for all ranges of BMI.

Weight and Body Mass Index for Predicting Thyroxine Dose in Primary Hypothyroidism

Background

The treatment of primary hypothyroidism with thyroxine is weight-based or body mass index (BMI)-based. However, significant variation in the dose and the consequent delay in achieving euthyroid state is observed along the spectrum of patient body weights.

Objectives

To determine the weight and BMI-based dosing of thyroxine in primary hypothyroidism to achieve euthyroidism.

Material and methods

It was a retrospective review of the patient records conducted in the department of endocrinology, Shifa International Hospital, Islamabad, from July 1, 2014, to June 30, 2019 (five-year period). Patients with clinical and biochemical hypothyroidism were enrolled and initiated on thyroxine replacement to achieve euthyroid status. A total of 504 patients were included in the study.

Results

The mean age was 44.5 ±13.6 standard deviation. Females were 83.5%. The mean dose of thyroxine to achieve euthyroid status was 107.7 ± 39.3 mean standard deviation mcg/day, i.e. 1.4 (0.5) mcg/kg/day. Euthyroid status was achieved in 264 (52.4%) of patients at three months. The mean TSH level after treatment was 2.09 (1.2) mU/L. The linear regression model showed that BMI and weight are independent predictors of the required thyroxine dose (R and Rsquare values are .274 and 0.075 for BMI and .319 and .102 for weight, respectively (P-value <.0001). There was no impact of age, gender, height, and duration of disease on achieving euthyroid at six months after treatment (P values: .85, .394, .827, and .105, respectively).

Conclusion

The optimum dose in primary hyperthyroidism can be determined with body weight and BMI-based calculations.

Patients on levothyroxine replacement in the community: association between hypothyroidism symptoms, co-morbidities and their quality of life

INTRODUCTION

Patients may be symptomatic, resulting in lower quality of life (QOL), despite L-thyroxine (LT4) therapy for hypothyroidism or having normal thyroid function. We hypothesized that their clinical symptoms of hypothyroidism and co-morbidities were associated with QOL.

OBJECTIVE

The study aimed to determine the association between the hypothyroid-related symptoms of Asian patients on LT4 treatment, their co-morbidities and their QOL.

METHOD

A questionnaire survey was conducted from November 2015 to July 2016 on consecutive multi-ethnic Asian patients on LT4 treatment for their hypothyroidism in a public primary care clinic in Singapore. Data on their demography, clinical symptoms, morbidity status, QOL scores based on the EQ5D instrument and thyroid function tests were computed and analysed, including logistic regression analysis to identify factors associated with lower QOL.

RESULTS

Complete data of 226 Asian patients (79.0% women; 74.2% Chinese, 10.0% Malay, 13.1% Indian and 2.6% other minority groups; median age 57 years; 27.5% had previous thyroid surgery) were analysed. Their QOL was not associated with their socio-demographic profiles, clinical parameters and latest thyroid-stimulating hormone and free thyroxine levels. Patients reporting weight gain, dry or coarse skin, leg swelling, feeling weak and carpal tunnel syndrome had significantly lower QOL; 53.6% of them with any single symptom had lower QOL. More patients had lower QOL if they had two or more symptoms and multiple medical conditions.

CONCLUSION

In Asian patients with hypothyroidism, weight gain, feeling tired, feeling weak, having dry or coarse skin, leg swelling and increased number of co-morbidities and symptoms were significantly associated with poorer QOL.