What is the initial treatment for a patient presenting with symptoms of hypothyroidism?

Initial Treatment for Hypothyroidism

For patients presenting with symptoms of hypothyroidism, levothyroxine (T4) therapy is the first-line treatment, with dosing based on patient characteristics and TSH levels. 1, 2

Diagnostic Confirmation

• Diagnosis of hypothyroidism requires laboratory confirmation with elevated TSH and low free T4 levels for overt hypothyroidism, or elevated TSH with normal free T4 for subclinical hypothyroidism 1, 3
• Morning serum hormone values provide the most accurate assessment of thyroid function 3
• Common symptoms include fatigue, weight gain, hair loss, cold intolerance, constipation, depression, voice changes, and dry skin 3, 4

Treatment Algorithm Based on TSH Levels

Overt Hypothyroidism (Elevated TSH, Low Free T4)

• Initiate levothyroxine therapy immediately upon diagnosis 2, 5
• For patients <70 years without cardiac disease or multiple comorbidities, start with full replacement dose of approximately 1.6 mcg/kg/day 1, 2
• For patients >70 years or with cardiac disease/multiple comorbidities, start with a lower dose of 25-50 mcg/day and titrate gradually 1, 6

Subclinical Hypothyroidism (Elevated TSH, Normal Free T4)

• For TSH >10 mIU/L: Initiate levothyroxine therapy regardless of symptoms 2, 7
• For TSH between 4.5-10 mIU/L: Treatment decisions should be individualized based on symptoms, presence of thyroid antibodies, and other risk factors 2, 8
• For symptomatic patients with any degree of TSH elevation: Consider a trial of levothyroxine 1, 8

Monitoring and Dose Adjustment

• Monitor TSH every 6-8 weeks while titrating hormone replacement to goal TSH within the reference range (0.5-2.5 mIU/L) 1, 2
• Once adequately treated, repeat testing every 6-12 months or if symptoms change 1, 2
• Free T4 can help interpret ongoing abnormal TSH levels during therapy, as TSH may take longer to normalize 1

Special Considerations

Central Hypothyroidism

• Central hypothyroidism presents with low TSH and low free T4, requiring different monitoring approach 1, 3
• When both adrenal insufficiency and hypothyroidism are present, steroids should always be started before thyroid hormone to avoid precipitating an adrenal crisis 1, 3

Pregnancy

• Women with hypothyroidism who become pregnant should increase their weekly dosage by 30% (take one extra dose twice per week) 6, 4
• Monitor TSH more frequently during pregnancy as requirements often increase 6
• Untreated maternal hypothyroidism may have adverse effects on fetal neurocognitive development 6

Common Pitfalls to Avoid

• Undertreatment risks include persistent hypothyroid symptoms, adverse effects on cardiovascular function, lipid metabolism, and quality of life 2
• Overtreatment can lead to iatrogenic hyperthyroidism, increasing risk for osteoporosis, fractures, abnormal cardiac output, and ventricular hypertrophy 2, 6
• About 25% of patients on levothyroxine are unintentionally maintained on doses sufficient to fully suppress TSH, highlighting the importance of regular monitoring 2
• Development of low TSH on therapy suggests overtreatment or recovery of thyroid function; dose should be reduced or discontinued with close follow-up 1, 2