Indications for Treating Subclinical Hypothyroidism
Treatment of subclinical hypothyroidism is strongly recommended for patients with TSH >10 mIU/L, pregnant women or those planning pregnancy, and should be considered in symptomatic patients with TSH between 4.5-10 mIU/L who have specific risk factors. 1
Definite Indications for Treatment
TSH >10 mIU/L: Patients with subclinical hypothyroidism and TSH levels consistently above 10 mIU/L should receive levothyroxine therapy due to higher risk of progression to overt hypothyroidism (5% per year) 1, 2
Pregnancy or planned pregnancy: All pregnant women with subclinical hypothyroidism should be treated regardless of TSH level to reduce risks of pregnancy complications (spontaneous abortion, gestational hypertension, pre-eclampsia, stillbirth) and potential adverse effects on fetal neurocognitive development 3, 2
Children and adolescents: Treatment is recommended due to possible adverse effects on growth and development 4
Consider Treatment in TSH 4.5-10 mIU/L with:
Symptomatic patients: Those with symptoms compatible with hypothyroidism may benefit from a trial of levothyroxine, though improvement should be carefully evaluated to distinguish from placebo effect 1
Positive TPO antibodies: Presence of antibodies indicates autoimmune etiology and higher risk of progression to overt hypothyroidism (4.3% vs 2.6% per year in antibody-negative individuals) 1, 4
Goiter: Presence of thyroid enlargement may indicate benefit from treatment 4, 5
Elevated cardiovascular risk: Some evidence suggests treatment may reduce cardiovascular events in patients under 65 years 6, 5
Infertility: Consider treatment in patients with fertility problems 4
Monitoring Without Treatment (TSH 4.5-10 mIU/L)
For patients with TSH between 4.5-10 mIU/L without the above risk factors, monitoring with thyroid function tests at 6-12 month intervals is recommended 1
Approximately 62% of mildly elevated TSH levels may normalize spontaneously when rechecked after 2 months 6
Age Considerations
Elderly patients (>85 years): Treatment of subclinical hypothyroidism with TSH up to 10 mIU/L should generally be avoided 2, 6
TSH goals are age-dependent: Upper limit of normal increases with age (3.6 mIU/L for <40 years, 7.5 mIU/L for >80 years) 6
Evaluation Before Treatment
Confirm diagnosis with repeat TSH and FT4 measurement after 2 weeks to 3 months 1
Evaluate for signs/symptoms of hypothyroidism, previous thyroid treatment, thyroid enlargement, and family history of thyroid disease 1
Review lipid profiles as subclinical hypothyroidism may affect cholesterol levels 1