Latent (subclinical) hyperthyroidism (synonyms: compensated hyperthyroidism; latent hyperthyroidism; latent hyperthyroidism; latent hyperthyroidism; subclinical hyperthyroidism; subclinical hyperthyroidism; ICD-10-GM E05.8: Other hyperthyroidism) refers to a “mild” hyperthyroidism that is usually manifested only by a change in the thyroid parameter TSH. The TSH value is then below 0.3 mU/l, with normal free T4 (fT4) at the same time.
Latent hyperthyroidism is considered persistent (persistent latent hyperthyroidism) if TSH control reproduces the initial value after three to six months.
The most common cause is pharmacotherapy (drug treatment) of hypothyroidism (underactive thyroid) (L-thyroxine overtherapy; 14-21% of cases).
Sex ratio: Women are more commonly affected than men.
Frequency peak: The frequency increases with increasing age.
The prevalence (disease incidence) is 0.7-2 % (in Germany). Iodine deficiency is of particular importance here.
The incidence (frequency of new cases) is in the range of 0.5-4.7 % .
Course and prognosis: In many cases, latent hyperthyroidism is discovered by chance during a laboratory examination. While treatment of latent hyperthyroidism was not considered necessary in the past, today the opposite is true: the risk of developing atrial fibrillation in old age is increased up to threefold in those affected. Furthermore, women with latent hyperthyroidism are more likely to develop osteoporosis (bone loss). One study showed that even latent hyperthyroidism increases mortality (the number of deaths in a given period, relative to the number of the population concerned) in the elderly by 41%. Men are particularly at risk here. In up to 8% of cases per year, latent hyperthyroidism develops into manifest hyperthyroidism. The annual conversion rate from latent to manifest hyperthyroidism is highly variable. It is reported to be 0.5-7%.
