Subclinical hypothyroidism (SCH) or “mild thyroid failure” is defined as elevated serum thyroid-stimulating hormone (TSH) in the presence of normal free thyroxine (T4). The incidence of SCH is estimated at 4.4-8.5% of the general population and occurs more frequently in women. Given that it falls below the diagnostic threshold, SCH is monitored rather than treated. Its management is a common topic of debate as SCH frequently progresses into overt hypothyroidism and is linked to long-term hyperlipidemia, endothelial dysfunction, cardiovascular disease, heart failure, and cerebrovascular disease. Premature hormone administration and lifestyle interventions have been explored as treatment options to mitigate the symptoms of SCH. Our review compares both modalities’ efficacy and potential for standardized clinical practice. A trial of levothyroxine demonstrated significant results in specific SCH demographics, such as patients who are pregnant or trying to conceive, those with goiter, those with thyroid peroxidase (TPO) antibody status, those with steadily increasing TSH, children, and adolescents. All other SCH patients presenting with chronic symptoms may also be reasonably considered for a three- to six-month trial of treatment. Lifestyle modifications through improved sleep hygiene, a diet within the recommended daily allowance (RDA) for iodine and selenium, increased exercise, and smoking cessation also proved efficacious. Our findings indicate that a synergistic approach to treatment is most favorable. Lifestyle modifications neither show adverse effects nor contraindications and can be safely recommended alone or alongside levothyroxine for the treatment of SCH.

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