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.

Introducción: La levotiroxina (LT4) se considera el estándar de tratamiento del hipotiroidismo. Las recomendaciones actuales sugieren una dosis de LT4 entre 1,6-1,8 µg/kg/día. El objetivo de este estudio fue evaluar la dosis de LT4 en pacientes adultos con hipotiroidismo primario de diferentes etiologías que alcanzaron el eutiroidismo. Métodos: Estudio transversal a partir de la revisión retrospectiva de historias clínicas de pacientes con hipotiroidismo primario en tratamiento con LT4. Los sujetos se clasificaron según el nivel de TSH en sobretratados (TSH<0,4 µUI/ml), eutiroideos (TSH 0,40-4,20) y subtratados (TSH>4,2) y según la etiología del hipotiroidismo. Se realizó un modelo de regresión logística escalonada para evaluar las variables asociadas con TSH <0,4 µUI/ml. Resultados: Se incluyeron 955 pacientes. El 75,13% tuvo un reemplazo adecuado de LT4. La dosis de LT4 para lograr el eutiroidismo fue mayor en pacientes con antecedentes de terapia con yodo radiactivo (1,92 µg/kg) y cirugía de tiroides (1,52 µg/kg), mientras que la dosis de LT4 para lograr el eutiroidismo en pacientes con tiroiditis de Hashimoto y tiroiditis atrófica fue menor que el reportado en estudios previos (1,25 y 1,08 µg/kg, respectivamente). Las variables que se asociaron con una mayor probabilidad de TSH<0,4 µUI/ml fueron el sexo masculino, tiroiditis de Hashimoto, terapia con yodo radiactivo y cirugía de tiroides. Conclusión principal: La dosis de LT4 necesaria para alcanzar el eutiroidismo en pacientes con hipotiroidismo varía según la etiología, siendo mayor en pacientes con hipotiroidismo por tratamiento con yodo radiactivo y cirugía tiroidea. Los pacientes con hipotiroidismo debido a tiroiditis de Hashimoto y tiroiditis atrófica requieren una dosis más baja que las recomendaciones actuales.

The influence of age and body weight on levothyroxine replacement dosage to achieve euthyroidism in patients with primary hypothyroidism.

INTRODUCTION: Although, it is generally held that the levothyroxine (LT4) dose tends to decrease with age, this theory remains controversial. Our objective was to assess whether the LT4 dose required to achieve euthyroid status varies according to age, body weight (BW), sex, menopausal status, or antibody status. MATERIALS AND METHODS: A cross-sectional study was performed from the retrospective review of the charts of patients with a previous diagnosis of primary hypothyroidism in treatment with LT4 and in a euthyroid state. Sex, age, actual body weight (ABW), TSH, and LT4 dose were recorded. Patients were grouped according to age ranges (18-44, 45-65, and over 65 years). A euthyroid state was defined as a serum TSH within the range of 0.4-4µIU/ml. A multiple linear regression model was performed to assess the LT4 dose and age, gender, antibody status, and ABW. RESULTS: A total of 882 charts of patients were reviewed. 586 patients met the inclusion criteria. The median age was 55 years. There was no correlation between the LT4 dose and age. A positive correlation was observed between the LT4 dose and ABW, but not with the ideal BW. Linear regression analysis showed that positivity antibody and ABW have a significant effect on the LT4 dose. Comparison of the LT4 dose between the different age groups showed no difference. CONCLUSION: Our study demonstrates that the dose of LT4 necessary to achieve euthyroidism is influenced by ABW and the presence of antibodies. Age and menopause did not influence the required daily dose of LT4.

The influence of age and body weight on levothyroxine replacement dosage to achieve euthyroidism in patients with primary hypothyroidism.

INTRODUCTION: Although, it is generally held that the levothyroxine (LT4) dose tends to decrease with age, this theory remains controversial. Our objective was to assess whether the LT4 dose required to achieve euthyroid status varies according to age, body weight (BW), sex, menopausal status, or antibody status. MATERIALS AND METHODS: A cross-sectional study was performed from the retrospective review of the charts of patients with a previous diagnosis of primary hypothyroidism in treatment with LT4 and in a euthyroid state. Sex, age, actual body weight (ABW), TSH, and LT4 dose were recorded. Patients were grouped according to age ranges (18-44, 45-65, and over 65 years). A euthyroid state was defined as a serum TSH within the range of 0.4-4µIU/ml. A multiple linear regression model was performed to assess the LT4 dose and age, gender, antibody status, and ABW. RESULTS: A total of 882 charts of patients were reviewed. 586 patients met the inclusion criteria. The median age was 55 years. There was no correlation between the LT4 dose and age. A positive correlation was observed between the LT4 dose and ABW, but not with the ideal BW. Linear regression analysis showed that positivity antibody and ABW have a significant effect on the LT4 dose. Comparison of the LT4 dose between the different age groups showed no difference. CONCLUSION: Our study demonstrates that the dose of LT4 necessary to achieve euthyroidism is influenced by ABW and the presence of antibodies. Age and menopause did not influence the required daily dose of LT4.

Hipoparatiroidismo y calcificaciones cerebrales: reporte de caso / Hypoparathyroidism and brain calcifications: a case report

Introducción. El hipoparatiroidismo es una enfermedad caracterizada por la ausencia o concentraciones inadecuadamente bajas de hormona paratiroidea (PTH), que conduce a hipocalcemia, hiperfosfatemia y excreción fraccional elevada de calcio en la orina. Las calcificaciones del sistema nervioso central son un hallazgo frecuente en estos pacientes. Caso clínico. Mujer de 56 años con antecedente de hipotiroidismo, que ingresó por un cuadro de 6 días de evolución caracterizado por astenia, parestesias periorales y movimientos anormales de manos y pies. Las pruebas de laboratorio demostraron hipocalcemia, hiperfosfatemia y niveles bajos de hormona paratiroidea. Se realizó una tomografía computarizada de cráneo que mostró áreas bilaterales y simétricas de calcificaciones en hemisferios cerebelosos, ganglios basales y corona radiata. No se evidenciaron trastornos en el metabolismo del cobre y hierro. Se estableció el diagnóstico del síndrome de Fahr secundario a hipoparatiroidismo y se inició tratamiento con suplementos de calcio y vitamina D con evolución satisfactoria. Discusión. El síndrome de Fahr es un trastorno neurológico caracterizado por el depósito anormal de calcio en áreas del cerebro que controlan la actividad motora. Se asocia a varias enfermedades, especialmente, hipoparatiroidismo. La suplementación con calcio y vitamina D con el objetivo de normalizar los niveles plasmáticos de estos cationes es el tratamiento convencional. (AU)

Introduction. Hypoparathyroidism is a disease characterized by absence or inappropriately low concentrations of circulating parathyroid hormone, leading to hypocalcaemia, hyperphosphataemia and elevated fractional excretion of calcium in the urine. Central nervous system calcifications are a common finding in these patients. Case report. 56-year-old woman with a history of hypothyroidism who was admitted for a 6-day course of illness characterized by asthenia, perioral paresthesias, and abnormal movements of the hands and feet. Laboratory tests showed hypocalcemia, hyperphosphatemia, and low parathyroid hormone levels. A cranial computed tomography was performed. It showed bilateral and symmetrical areas of calcifications in the cerebellar hemispheres, basal ganglia, and radiata crown. No disorders of copper or iron metabolism were evident. The diagnosis of Fahr syndrome secondary to hypoparathyroidism was established and treatment with calcium and vitamin D supplements was started with satisfactory evolution. Discussion. Fahr's syndrome is a neurological disorder associated with abnormal calcium deposition in areas of the brain that control motor activity. It is associated with various diseases, especially hypoparathyroidism. The conventional treatment is supplementation with calcium and vitamin D, with the aim of normalizing their plasma levels. (AU)