Información del artículo
La elevación de la concentración de tirotropina (TSH), en presencia de concentraciones normales de hormonas tiroideas circulantes, define la situación de hipotiroidismo subclínico. La prevalencia de este trastorno hormonal es elevada en la población general, y es especialmente destacable en mujeres mayores. La historia natural del hipotiroidismo subclínico se ha evaluado en algunos estudios epidemiológicos y en estudios sistemáticos que han estudiado la tasa de incidencia y los factores de riesgo para la progresión a hipotiroidismo franco. La progresión a hipofunción manifiesta tiene lugar entre un 3,3 y un 11,4% de los pacientes por año. Esta tasa de incidencia es superior en mujeres, en pacientes de mayor edad y en los que presentan bocio, síntomas de hipotiroidismo o elevación de la cifra de anticuerpos antitiroideos. Sin embargo, la concentración inicial de TSH es el factor de riesgo más importante en la evaluación del riesgo de progresión a hipofunción tiroidea franca. El tratamiento con levotiroxina en pacientes con hipotiroidismo subclínico evita la progresión a hipotiroidismo franco y puede producir mejoría sintomática, mejoría en el perfil lipídico y, en consecuencia, reducción del riesgo cardiovascular. Dado que el tratamiento es de por vida y tiene riesgos, debe evaluarse cuidadosamente y de forma individualizada a los pacientes antes de tomar la decisión de iniciar la terapia sustitutiva. Actualmente, se recomienda el tratamiento sustitutivo en los pacientes con concentraciones de TSH superiores a 10 mU/l. En los pacientes con concentraciones entre 5 y 10 mU/l, la observación periódica es un buen método para conocer la tendencia a la progresión o a la estabilidad de las cifras de TSH.
Palabras clave:
Hipotiroidismo subclínico
Historia natural
Disfunción tiroidea subclínica
Tirotropina
Levotiroxina
Subclinical hypothyroidism is defined by elevated serum thyrotropin (TSH) levels in the presence of normal concentrations of circulating thyroid hormones. The prevalence of this hormonal alteration is high in the general population, especially in elderly women. The natural history of subclinical hypothyroidism has been assessed in several epidemiological surveys and, more recently, in systematic studies aimed at evaluating the incidence rate and risk factors for the development of definitive thyroid failure. In general, the mean annual rate of progression to overt hypothyroidism ranges from 3.3 to 11.4% per year. This incidence rate is higher in women, elderly patients, and those who have goiter, symptoms of hypothyroidism, or a positive thyroid autoantibody titer. However, the main factor in the evaluation of the risk of progression to overt thyroid failure is the initial TSH concentration. Treatment with levothyroxine in patients with subclinical hypothyroidism prevents the development of overt hypothyroidism and may improve symptoms and lipid profile, thus decreasing cardiovascular risk. Since this therapy is lifelong and is not problem free, careful and individualized evaluation of each patient should be performed before prescribing replacement therapy. Present recommendations include replacement therapy in patients with TSH levels greater than 10 mUI/L. In patients with serum TSH levels between 5 and 10 mUI/L periodic follow-up may be satisfactory to evaluate the tendency towards progression or stability of TSH levels.
Key words:
Subclinical hypothyroidism
Natural history
Subclinical thyroid dysfunction
Thyrotropin
Levothyroxine
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