What are the latest guidelines for treating hyperthyroidism (overactive thyroid) and hypothyroidism (underactive thyroid)?

Latest Guidelines for Treating Hyperthyroidism and Hypothyroidism

The most current guidelines recommend standard thyroid hormone replacement therapy (levothyroxine) for hypothyroidism, while hyperthyroidism treatment should follow a disease-specific approach using antithyroid medications, radioactive iodine, or surgery based on etiology and patient factors. 1

Diagnosis and Evaluation

Initial Testing

• TSH is the primary screening test for thyroid dysfunction, with follow-up testing of free T4 levels in persons with persistently abnormal TSH to differentiate between subclinical and overt thyroid dysfunction 1
• Multiple tests should be done over a 3-6 month interval to confirm abnormal findings 1
• For hyperthyroidism evaluation, TSH receptor antibodies, thyroid peroxidase antibodies, thyroid ultrasonography, and scintigraphy help determine the specific cause 2

Management of Hypothyroidism

Treatment Approach

• Standard thyroid replacement therapy with levothyroxine is the principal treatment for hypothyroidism 1, 3
• Initial dosing recommendations:
  • Young, healthy patients: Full dose (1.6 mcg/kg) 1
  • Elderly patients with cardiovascular disease: Reduced dose of 25-50 mcg 1

Monitoring and Dose Adjustment

• Repeat TSH and free T4 testing after 6-8 weeks and adjust thyroid hormone dose accordingly 1
• If TSH remains above reference range, increase thyroid hormone dose by 12.5-25 mcg 1
• After identifying appropriate maintenance dose, further evaluation is required yearly or sooner if patient's status changes 1

Special Considerations

• Patients should take levothyroxine as a single dose on an empty stomach, 30-60 minutes before breakfast with a full glass of water 3
• Avoid taking levothyroxine within 4 hours of agents that decrease absorption (iron, calcium supplements, antacids) 3
• Patients with diabetes should monitor blood/urinary glucose levels as directed, as thyroid replacement may affect glycemic control 3

Management of Hyperthyroidism

Treatment Options Based on Etiology

Graves' Disease

• Antithyroid drugs (methimazole or propylthiouracil) are preferred as first-line treatment 2
• Methimazole is the drug of choice due to its longer half-life and fewer severe side effects, except during first trimester of pregnancy 4
• Treatment duration: 12-18 months (standard course) or 5-10 years (long-term approach with fewer recurrences) 2
• Recurrence occurs in approximately 50% of patients after standard 12-18 month course 2

Toxic Nodular Goiter

• Primarily treated with radioactive iodine (131I) or thyroidectomy 2
• Radiofrequency ablation is a less common alternative 2

Thyroiditis

• Usually self-limiting with two phases 1
• In the hyperthyroid phase, symptomatic patients may benefit from beta blockers (e.g., atenolol 25-50 mg daily) 1
• Monitor closely with regular symptom evaluation and free T4 testing every 2 weeks 1
• Introduce thyroid hormones if the patient becomes hypothyroid (low free T4/T3) 1

Treatment Based on Severity

Mild Hyperthyroidism (TSH 0.1-0.45 mIU/L)

• Standard therapy should be followed 1
• The panel recommends against routine treatment for all patients with mildly decreased TSH (0.1-0.45 mIU/L) 1

Moderate to Severe Hyperthyroidism (TSH <0.1 mIU/L)

• Treatment should be considered for subclinical hyperthyroidism with TSH <0.1 mIU/L due to Graves' or nodular thyroid disease 1
• Hold immunotherapy for ≥ grade 3 immune-related adverse events if applicable 1

Special Populations

Pregnancy

• Hyperthyroidism in pregnant women is treated with a thioamide (propylthiouracil or methimazole) 1
• Propylthiouracil is preferred during first trimester due to potential fetal abnormalities with methimazole 5
• Consider switching from propylthiouracil to methimazole for second and third trimesters due to potential maternal hepatotoxicity from propylthiouracil 5
• Goal: Maintain FT4 or FTI in high-normal range using lowest possible thioamide dosage 1
• Monitor FT4 or FTI every 2-4 weeks 1
• Hypothyroidism in pregnant women is treated with levothyroxine in sufficient dosage to normalize TSH 1
• Adjust dosage every four weeks until TSH is stable; check TSH every trimester 1

Monitoring and Follow-up

Hyperthyroidism

• Monitor thyroid function regularly during treatment 1
• For thyroiditis, monitor closely with regular symptom evaluation and free T4 testing every 2 weeks 1
• For persistent thyrotoxicosis (>6 weeks), consider endocrine consultation for additional workup 1

Hypothyroidism

• After starting treatment, repeat TSH and free T4 testing after 6-8 weeks 1
• After identification of appropriate maintenance dose, further evaluation yearly or sooner if patient's status changes 1

Potential Complications and Side Effects

Antithyroid Medications

• Propylthiouracil: Risk of liver damage (particularly in pediatric population), agranulocytosis, vasculitis 5
• Patients should report symptoms of hepatic dysfunction (anorexia, pruritus, jaundice, etc.) particularly in first six months of therapy 5
• Patients should immediately report evidence of illness, particularly sore throat, skin eruptions, fever, headache, or general malaise 5

Levothyroxine

• Patients should notify healthcare provider if experiencing: rapid or irregular heartbeat, chest pain, shortness of breath, nervousness, irritability, tremors, weight changes, heat intolerance, or other unusual events 3
• Partial hair loss may occur rarely during first few months of therapy but is usually temporary 3

Long-term Outcomes

• Long-term continuous methimazole treatment has shown better outcomes in mood, cognition, cardiac function compared to radioactive iodine therapy in patients with diffuse toxic goiter 6
• Hyperthyroidism is associated with increased mortality; prognosis might be improved by rapid and sustained control 2