Latent (subclinical) hypothyroidism (SCH; synonyms: compensated hypothyroidism; latent hypothyroidism; latent hypothyroidism; latent hypothyroidism; subclinical hypothyroidism; ICD-10-GM E03. 9: Hypothyroidism, unspecified) refers to a “mild” hypothyroidism that is usually manifested only by a change in the thyroid parameter TSH: TSH > 4 mU/l, with a concomitant normal fT4 level.
If TSH is higher than 10 mU/L and fT4 is normal, the disorder is evaluated as “severe” latent hypothyroidism (grade 2 hypothyroidism).
The disorder is dependent on iodine supply. In regions poorly supplied with iodine, the proportion is relatively low.
Sex ratio: Women more often than men
Frequency peak: The disease occurs predominantly after the age of 60.
The prevalence (disease frequency) is 3-16% (in Germany), depending on the geographical location; the prevalence is particularly high in women older than 60 years. In pregnant women, the prevalence is 2.5-5% (estimated). They must be treated in any case.
Course and prognosis: The therapy of adults with latent hypothyroidism is currently controversial (see below drug therapy). In children, latent hypothyroidism is always treated because of the possible consequences such as short stature.In a larger randomized controlled trial, L-thyroxine substitution did not improve symptoms in seniors (> 65 years) with subclinical hypothyroidism. Furthermore, there was no detectable effect on blood pressure or body weight. Note: Low elevated TSH levels without antibodies to thyroperoxidase (TPO) showed a high rate of spontaneous normalization of TSH levels.In 5% of cases per year, latent hypothyroidism develops into manifest hypothyroidism.
