What is the treatment for hypothyroidism with a Thyroid-Stimulating Hormone (TSH) level of 14?

Treatment for TSH Level of 14 mIU/L

Initiate levothyroxine therapy immediately for a TSH of 14 mIU/L, as this level represents overt hypothyroidism requiring treatment regardless of symptoms. 1

Confirmation and Initial Assessment

• Confirm the diagnosis with measurement of both TSH and free T4 to distinguish between subclinical hypothyroidism (normal free T4) and overt hypothyroidism (low free T4). 1
• A TSH of 14 mIU/L is well above the treatment threshold of 10 mIU/L, where levothyroxine therapy is recommended regardless of symptoms due to approximately 5% annual risk of progression to more severe hypothyroidism. 1, 2
• Consider measuring anti-TPO antibodies to confirm autoimmune etiology (Hashimoto's thyroiditis), which predicts higher progression risk (4.3% per year vs 2.6% in antibody-negative individuals). 1

Levothyroxine Dosing Strategy

For patients under 70 years without cardiac disease:

• Start with full replacement dose of approximately 1.6 mcg/kg/day administered once daily. 1
• This approach allows faster normalization of thyroid function in younger, otherwise healthy patients. 1

For patients over 70 years or with cardiac disease/multiple comorbidities:

• Start with a lower dose of 25-50 mcg/day and titrate gradually. 1, 3
• Elderly patients with coronary disease are at increased risk of cardiac decompensation, angina, or arrhythmias even with therapeutic levothyroxine doses. 2
• Increase the dose by 12.5-25 mcg every 6-8 weeks based on TSH response. 1

Monitoring Protocol

• Recheck TSH and free T4 in 6-8 weeks after initiating therapy or any dose adjustment. 1, 3
• Target TSH should be within the reference range of 0.5-4.5 mIU/L, ideally in the lower half (0.4-2.5 mIU/L) for most adults. 1, 4
• Once adequately treated with stable TSH levels, repeat testing every 6-12 months or whenever symptoms change. 1, 3
• Free T4 can help interpret ongoing abnormal TSH levels during therapy, as TSH may take longer to normalize. 1

Special Population Considerations

Pregnant women or those planning pregnancy:

• For new onset hypothyroidism with TSH ≥10 mIU/L, start levothyroxine at 1.6 mcg/kg/day. 3
• Monitor TSH every 4 weeks during pregnancy and adjust dosage to maintain TSH within trimester-specific reference ranges. 3
• Inadequate treatment during pregnancy is associated with preeclampsia, low birth weight, and potential neurodevelopmental effects in offspring. 1

Pediatric patients:

• Rapid restoration of normal serum T4 concentrations is essential for preventing adverse effects on cognitive development and physical growth. 3
• Monitor TSH and total or free-T4 at 2 and 4 weeks after initiation, 2 weeks after any dose change, then every 3-12 months following stabilization. 3

Critical Pitfalls to Avoid

• Never start thyroid hormone before ruling out adrenal insufficiency in patients with suspected central hypothyroidism, as this can precipitate adrenal crisis. 1
• Avoid excessive dose increases that could lead to iatrogenic hyperthyroidism, which increases risk for osteoporosis, fractures, atrial fibrillation, and cardiac complications. 1, 2
• Approximately 25% of patients on levothyroxine are unintentionally maintained on doses sufficient to fully suppress TSH, significantly increasing morbidity risks. 1
• Do not adjust doses more frequently than every 6-8 weeks, as levothyroxine requires this time to reach steady state. 1

Risks of Undertreatment

• Persistent hypothyroid symptoms including fatigue, weight gain, cold intolerance, and constipation. 1
• Adverse effects on cardiovascular function, with subclinical hypothyroidism associated with delayed relaxation and abnormal cardiac output. 1
• Negative impact on lipid metabolism, with potential elevation of LDL cholesterol. 1, 2
• Decreased quality of life and potential cognitive impairment if left untreated. 1

Long-term Management

• Once the appropriate maintenance dose is established, continue lifelong levothyroxine therapy with annual TSH monitoring. 1, 2
• Development of low TSH on therapy suggests overtreatment or recovery of thyroid function; dose should be reduced with close follow-up. 1
• If TSH remains elevated despite apparent adequate replacement dose, assess for poor compliance, malabsorption, drug interactions, or timing of administration. 3, 2