Subclinical thyroid dysfunction - whether and when to treat?

Subclinical thyroid dysfunction consists of subclinical hypothyroidism (SHYPO) and hyperthyroidism (SHYPERJ, among which SHYPO is the most common. Subclinical thyroid dysfunctions are associated with more frequent progression to overt thyroid dysfunctions than in healthy population, elevated risk of cardiovascular end-points and increased mortality. SHYPO is associated with complications of pregnancy and infertility. SHYPER is associated with increased frequency of cardiac arrhytmias and with decreased bone mass density, particularly in postmenopausal women. Thus subclinical thyroid dysfunctions require early diagnosis as to indication and introduction of therapy. TSH level and clinical manifestation of thyroid dysfunction are also important for recommendation for therapy. All adverse effects of SHYPO and SHYPER are present usually in patients with extreme TSH levels (> 10 ulU/ml and < 0.1 ulU/ml respectively). There are ongoing debates about treatment of patient with only moderately altered TSH levels. There is not sufficient evidence to recommend routine treatment for patient with SHYPO and TSH < 10 ulU/ml and SHYPER in young asymptomatic patients with TSH 0.1-0.5 ulU/ml; periodic monitoring and individualization of therapy is suggested. In case of exogenous SHYPER due to intentional suppression of TSH with levothyroxine in case of differentiated thyroid carcinoma, periodic assessment of patients and maintenance of optimal TSH levels is required.