Update on subclinical thyroid dysfunction

Abstract

Subclinical thyroid dysfunction is defined by serum thyroid-stimulating hormone (TSH) levels either greater or less than the reference range with normal thyroxine (T4) concentrations, and consists of subclinical hypothyroidism (SCH) and subclinical hyperthyroidism (SCHyper). For the proper diagnosis of SCH, it is most important to be able to correctly evaluate the serum TSH levels, which have numerous unique characteristics. We also need to be versed in TSH harmonization, which was recently launched world-wide. In this review, we will attempt to determine the best clinical approaches to the treatment of subclinical thyroid dysfunction based on recent guidelines published from several countries and novel findings of several recent large-scale clinical studies.

Impact of metformin on hypothalamic–pituitary–thyroid axis activity in women with autoimmune and non-autoimmune subclinical hypothyroidism: a pilot study

“…Although subclinical hypothyroidism is characterized by TSH above the upper limit of normal coexisting with normal free thyroxine [ 21 , 22 ], our study included only patients with TSH levels not exceeding 7.5 mU/L. This cut-off value was selected to not enroll subjects requiring levothyroxine therapy.…”

“…This cut-off value was selected to not enroll subjects requiring levothyroxine therapy. Although indications for thyroid hormone substitution are TSH concentrations above 10 mIU/L [ 21 , 23 ], levothyroxine treatment may or should be considered in patients with milder forms of hypothyroidism (repeated measurements of TSH between the upper limit of normal and 10 mIU/L), if they have symptoms suggestive of hypothyroidism, are TPOAb-positive or plan to conceive [ 22 , 24 ]. Because the percentage of symptomatic patients with subclinical hypothyroidism and the severity of these symptoms correlate with TSH levels [ 23 ], the probability of thyroid hormone substitution is lower in patients with TSH concentrations between 4.5 and 7.5 mIU/L than in individuals with TSH above 7.5 mIU/L.…”

Diagnóstico y tratamiento del hipotiroidismo subclínico en adultos mayores

“…Cuando existe la presencia de obesidad, TSH > 10 mUI/L y TPOAb positivo, indicarán hipotiroidismo subclínico, en cambio, si solo existe obesidad, hay que tener en cuenta que esto puede elevar los valores de TSH (Hashimoto, 2022;Palacio et al, 2017;Yoo & Chung, 2021).…”

“…Para poder diagnosticar el hipotiroidismo subclínico, la TSH deben ser > 4,0 mUI/L y T4 libre en rangos normales. Cuando se detecta esta alteración, se debe volver a realizar otra prueba de TSH entre 1 a 3 meses para poder hacer un diagnóstico certero de hipotiroidismo subclínico (Alzahrani et al, 2020;Hashimoto, 2022). Con respecto a los pacientes mayores de edad, las enfermedades de base que presentan y la polifarmacia pueden hacer que se dé una mala interpretación en los resultados del perfil tiroideo (Borzi et al, 2020).…”

The relationship between thyroid hormones and lipid profile in subclinical hypothyroidism female patients

“…Subclinical thyroid disease is characterized as subclinical hyperthyroidism and subclinical hypothyroidism (SHT). 2 The former one occurs when serum TSH concentrations are low while T 4 and T 3 concentrations are normal, and subclinical hypothyroidism occurs when serum TSH concentrations are elevated but serum thyroid hormones concentrations are normal. 3 The incidence of thyroid dysfunctions in the general population could be due to many reasons, such as ethnic, age and geographical factors as well as iodine intake.…”