How much levothyroxine (T4) is contained in a 15 mg tablet of Armour Thyroid (desiccated porcine thyroid)?

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Contenido de T4 en Armour Thyroid 15 mg

Un comprimido de 15 mg (1/4 de grano) de Armour Thyroid contiene aproximadamente 9.5 mcg de levotiroxina (T4). 1

Composición Estándar de Armour Thyroid

Según la etiqueta oficial de la FDA, cada grano (aproximadamente 60-65 mg) de Armour Thyroid proporciona 38 mcg de levotiroxina (T4) y 9 mcg de liotironina (T3) 1. Esta preparación de tiroides desecada porcina mantiene una proporción T4:T3 de aproximadamente 4:1 por peso 2.

Cálculo para 15 mg

Para calcular el contenido de T4 en 15 mg:

  • 1 grano = ~60 mg = 38 mcg de T4
  • 15 mg = 1/4 de grano
  • 15 mg contiene: 38 mcg ÷ 4 = 9.5 mcg de T4
  • 15 mg también contiene: 9 mcg ÷ 4 = 2.25 mcg de T3

Consideraciones Clínicas Importantes

Variabilidad entre lotes: El contenido hormonal y la proporción T4:T3 pueden variar en las preparaciones de tiroides desecada dependiendo de la marca empleada y si es de origen porcino o bovino 2. Estudios de investigación han mostrado variaciones de hasta 10% entre diferentes lotes 3.

Diferencias con levotiroxina sintética: A diferencia de la levotiroxina sintética (donde aproximadamente el 80% del T3 periférico proviene de la conversión de T4), Armour Thyroid proporciona T3 preformado, lo que resulta en niveles séricos de T3 más altos y niveles de T4 más bajos comparado con monoterapia de levotiroxina 4.

Advertencia sobre el uso clínico: Las guías de práctica clínica de AACE/ATA indican que la tiroides desecada no ha sido sistemáticamente estudiada 2. La levotiroxina sintética permanece como el tratamiento de primera línea para hipotiroidismo según las guías internacionales 5, 6.

References

2
Guideline

clinical practice guidelines for hypothyroidism in adults: cosponsored by the american association of clinical endocrinologists and the american thyroid association.

Endocrine practice : official journal of the American College of Endocrinology and the American Association of Clinical Endocrinologist, 2012

3
Research

Triiodothyronine and thyroxine content of desiccated thyroid tablets.

Metabolism: clinical and experimental, 1977

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