What is the recommended treatment for hypothyroidism?

Hypothyroidism Treatment

Levothyroxine monotherapy is the standard treatment for hypothyroidism, with dosing of approximately 1.6 mcg/kg/day for patients under 70 years without cardiac disease, or 25-50 mcg/day for elderly patients or those with cardiac disease, titrated to normalize TSH levels. 1, 2

Initial Treatment Selection

• Levothyroxine (T4) is the first-line and only recommended thyroid hormone replacement therapy for hypothyroidism. 1, 3
• Combination therapy with levothyroxine plus liothyronine (T3) should not be used routinely, as no clear advantages have been demonstrated and levothyroxine monotherapy remains the treatment of choice. 4
• Treatment should be initiated immediately upon diagnosis to prevent serious complications including heart failure, cardiovascular events, and myxedema coma (which carries up to 30% mortality). 3

Dosing Algorithm Based on Patient Characteristics

For Patients Under 70 Years Without Cardiac Disease

• Start with full replacement dose of 1.6 mcg/kg/day, which is safe and more convenient than gradual titration. 1, 2, 5
• This approach reaches euthyroidism faster without increased cardiac risk in cardiac asymptomatic patients. 5
• Full-dose initiation is cost-effective and avoids prolonged periods of inadequate treatment. 5

For Elderly Patients (>70 Years) or Those With Cardiac Disease

• Start with 25-50 mcg/day and titrate gradually to avoid cardiac complications. 1, 2, 6
• Elderly patients have increased prevalence of cardiovascular disease and are at higher risk for atrial arrhythmias, particularly atrial fibrillation with overtreatment. 6
• Use smaller dose increments (12.5 mcg) in this population to prevent cardiac decompensation. 1

For Patients With Long-Standing Severe Hypothyroidism

• Start with lower doses (25-50 mcg/day) regardless of age, as rapid normalization can unmask or worsen cardiac ischemia. 7
• Titrate gradually with close monitoring for cardiac symptoms. 7

Monitoring Protocol

• Check TSH every 6-8 weeks during dose titration until target TSH is achieved. 1, 2, 3
• Target TSH should be within the reference range of 0.5-4.5 mIU/L (or 0.4-4.0 mIU/L per some guidelines). 8, 7
• Once adequately treated, repeat TSH testing every 6-12 months or if symptoms change. 1
• Free T4 can help interpret ongoing abnormal TSH levels during therapy, as TSH may take longer to normalize. 1

Dose Adjustment Strategy

• Adjust levothyroxine in increments of 12.5-25 mcg based on current dose and patient characteristics. 1
• Larger adjustments (25 mcg) may be appropriate for younger patients without cardiac disease. 1
• Smaller adjustments (12.5 mcg) should be used for elderly patients or those with cardiac disease. 1
• Wait 6-8 weeks between dose adjustments to reach steady state before reassessing. 1

Special Population Considerations

Pregnancy

• Levothyroxine should not be discontinued during pregnancy and hypothyroidism diagnosed during pregnancy should be promptly treated. 6
• TSH should be monitored and levothyroxine dosage adjusted during pregnancy, as requirements typically increase by 25-50%. 6
• Untreated maternal hypothyroidism is associated with spontaneous abortion, gestational hypertension, pre-eclampsia, stillbirth, premature delivery, and adverse effects on fetal neurocognitive development. 6
• Women planning pregnancy require more aggressive TSH normalization, as subclinical hypothyroidism is associated with adverse pregnancy outcomes. 1, 2
• Return to pre-pregnancy dose immediately after delivery, as postpartum TSH levels are similar to preconception values. 6

Lactation

• Levothyroxine is present in human milk but no adverse effects on breastfed infants have been reported. 6
• Adequate levothyroxine treatment during lactation may normalize milk production in hypothyroid lactating mothers. 6

Pediatric Patients

• Initiate levothyroxine therapy immediately upon diagnosis in children to prevent adverse effects on cognitive development and physical growth. 6
• Levothyroxine is generally continued for life in pediatric patients with congenital hypothyroidism. 6
• Closely monitor infants during the first 2 weeks of therapy for cardiac overload and arrhythmias. 6

Patients With Concurrent Adrenal Insufficiency

• Always start corticosteroids before initiating or increasing levothyroxine in patients with suspected central hypothyroidism or concurrent adrenal insufficiency to prevent adrenal crisis. 1

Critical Pitfalls to Avoid

• Approximately 25% of patients on levothyroxine are unintentionally maintained on doses sufficient to fully suppress TSH, increasing risks for atrial fibrillation, osteoporosis, fractures, abnormal cardiac output, and ventricular hypertrophy. 1, 2
• Overtreatment with levothyroxine increases risk for atrial fibrillation (especially in elderly), osteoporosis, fractures, and cardiovascular complications. 1
• Undertreatment risks persistent hypothyroid symptoms, adverse cardiovascular effects, abnormal lipid metabolism, and reduced quality of life. 1
• Do not treat based on a single elevated TSH value, as 30-60% of elevated TSH levels normalize spontaneously on repeat testing. 1
• Never start thyroid hormone before ruling out adrenal insufficiency in patients with suspected central hypothyroidism. 1
• Adjusting doses too frequently before reaching steady state (should wait 6-8 weeks between adjustments) leads to suboptimal management. 1

Treatment Goals and Outcomes

• Normalization of TSH levels improves clinical manifestations including fatigue, weight gain, cognitive issues, menstrual irregularities, and cardiovascular function. 3
• Proper treatment reduces risk of cardiovascular events, heart failure, and progression to myxedema coma. 3
• Treatment improves female reproductive health by restoring ovulation and reducing infertility and miscarriage risk. 3
• In patients with diabetes, adequate treatment helps normalize insulin resistance and hyperglycemia. 3