What is the initial evaluation and treatment for a patient presenting with hypothyroid symptoms?

Initial Evaluation and Treatment for Hypothyroidism

The initial evaluation for a patient presenting with hypothyroid symptoms should include TSH and free T4 testing, followed by treatment with levothyroxine at a dose of 1.5-1.8 mcg/kg/day for most young patients, with lower starting doses for elderly patients or those with cardiovascular disease. 1, 2

Diagnostic Evaluation

Initial Laboratory Testing

• TSH is the preferred initial test for suspected primary hypothyroidism 3
• If TSH is abnormal, free T4 should be measured to further narrow the diagnosis 3
• Morning serum hormone values are required for accurate assessment 4
• Consider testing for thyroid antibodies such as thyroid peroxidase (TPO) antibody if hypothyroidism is confirmed 5

Clinical Presentation

• Common symptoms include fatigue, weight gain, hair loss, cold intolerance, constipation, depression, voice changes, and dry skin 4, 1
• More advanced symptoms may include intellectual slowness, insomnia, and with progression, myxedema 4
• Signs and symptoms are often nonspecific, especially early in the disease, making laboratory confirmation essential 1

Differential Diagnosis

• Primary hypothyroidism (thyroid gland dysfunction) - most common 5
• Secondary/central hypothyroidism (pituitary or hypothalamic disease) 5
• Subclinical hypothyroidism (elevated TSH with normal free T4 and T3) 5

Treatment Approach

Levothyroxine Therapy

• Levothyroxine (LT4) monotherapy is the current standard for management of both primary and central hypothyroidism 5
• Starting dose recommendations:
  • Young, otherwise healthy patients: 1.5-1.8 mcg/kg/day 1
  • Patients >60 years or with known/suspected heart disease: 12.5-50 mcg/day 1
  • Elderly patients with multiple comorbidities: Start at lower doses and titrate gradually 5

Dose Titration

• Repeat TSH and free T4 testing 6-8 weeks after initiation of therapy or after any dose change 2
• Target TSH level for primary hypothyroidism: 0.5-2.0 mIU/L 5
• For central hypothyroidism, maintain free T4 levels in the upper half of the normal range 5
• After identifying appropriate maintenance dose, evaluate clinical and biochemical response every 6-12 months 2

Special Populations

• Pregnant patients:
  • Increase weekly levothyroxine dosage by 30% (take one extra dose twice weekly) 1
  • Monitor TSH every 4 weeks until stable dose is reached 2
  • Maintain TSH in trimester-specific reference range 2
• Patients with coronary artery disease:
  • Start at lower doses (12.5-25 mcg/day) and increase gradually 5

Management of Subclinical Hypothyroidism

Treatment Indications

• All patients with TSH >10 mIU/L should be treated 5, 6
• For TSH between 4.0-10.0 mIU/L, treatment should be considered for:
  • Symptomatic patients 6
  • Pregnant women or those planning pregnancy 5
  • Patients with positive TPO antibodies 5, 6
  • Patients with goiter 5
• Consider avoiding treatment in patients >85 years with TSH ≤10 mIU/L 5, 6

Monitoring Response

• For patients started on levothyroxine for symptoms attributed to subclinical hypothyroidism, assess response 3-4 months after reaching target TSH 6
• If no symptom improvement occurs, consider discontinuing therapy 6

Common Pitfalls and Caveats

• Central hypothyroidism may present with low TSH and low free T4, requiring different monitoring approach 4
• When both adrenal insufficiency and hypothyroidism are present, steroids should always be started before thyroid hormone to avoid precipitating an adrenal crisis 4
• Poor compliance, malabsorption, and drug interactions should be considered in patients with persistently elevated TSH despite adequate replacement dose 5
• Over-replacement is common and associated with increased risk of atrial fibrillation and osteoporosis 5
• Adding T3 (triiodothyronine) is not recommended, even in patients with persistent symptoms and normal TSH levels 1

By following this systematic approach to evaluation and treatment, most patients with hypothyroidism can achieve symptom relief and normalized thyroid function.