What is the treatment approach for a patient with hyperthyroidism (low TSH) and Polycystic Ovary Syndrome (PCOS)?

Management of Low TSH and PCOS

Treat the hyperthyroidism and PCOS as separate conditions, addressing the hyperthyroidism first with beta-blockers for symptom control and definitive therapy (antithyroid drugs, radioactive iodine, or surgery), while managing PCOS with standard therapies once thyroid function is controlled.

Initial Assessment and Diagnosis

Confirm the diagnosis of hyperthyroidism by measuring TSH, free T4, and free T3 to establish the degree of thyroid hormone excess 1, 2. The low TSH with elevated thyroid hormones confirms hyperthyroidism, which requires immediate attention due to its impact on cardiovascular function, bone health, and overall mortality 3.

• Determine the etiology of hyperthyroidism through TSH-receptor antibodies, thyroid peroxidase antibodies, thyroid ultrasonography, and scintigraphy 2
• The most common causes are Graves' disease (70%), toxic nodular goiter (16%), subacute thyroiditis (3%), or drug-induced (9%) 2
• Physical examination findings of ophthalmopathy or thyroid bruit are diagnostic of Graves' disease and warrant early endocrine referral 4

Immediate Symptom Management

Start beta-blocker therapy immediately (atenolol or propranolol) for symptomatic relief of tachycardia, tremor, anxiety, and other cardiovascular manifestations regardless of severity 4, 5. This is critical because hyperthyroidism increases cardiac workload and can precipitate heart failure, especially in patients with underlying cardiac disease 4.

• Beta-blockers rapidly improve cardiac, neurologic, and other symptoms while definitive treatment takes effect 4
• Continue beta-blockers until thyroid function normalizes 5

Definitive Treatment Algorithm for Hyperthyroidism

For Graves' Disease:

First-line treatment is antithyroid drugs (methimazole preferred over propylthiouracil) for 12-18 months to induce remission 1, 6, 2. Methimazole inhibits thyroid hormone synthesis without affecting existing circulating hormones 7.

• Approximately 50% of patients experience recurrence after stopping antithyroid drugs 2
• Risk factors for recurrence include age <40 years, FT4 ≥40 pmol/L, TSH-binding inhibitory immunoglobulins >6 U/L, and goiter size ≥WHO grade 2 2
• Long-term antithyroid drug therapy (5-10 years) reduces recurrence to 15% compared to 50% with short-term treatment 2

Alternative definitive therapies:

• Radioactive iodine ablation is the most widely used treatment in the United States and is well-tolerated 1, 6
• Avoid radioactive iodine in Graves' disease with ophthalmopathy, as it may worsen eye disease 6, 5
• Surgery (total thyroidectomy) is indicated for concurrent thyroid cancer, pregnancy, compressive symptoms, or Graves' ophthalmopathy 5

For Toxic Nodular Goiter:

Radioactive iodine or thyroidectomy is the treatment of choice, as antithyroid drugs will not cure this condition 6, 2.

For Thyroiditis:

Observation with supportive care is appropriate, as thyroiditis-induced hyperthyroidism is self-limited and typically resolves within weeks 4. Monitor thyroid function every 2-3 weeks to detect transition to hypothyroidism, which is the most common outcome 4.

Monitoring During Hyperthyroidism Treatment

• Check thyroid function (TSH, FT4) every 2-3 weeks after diagnosis until stable 4
• For persistent thyrotoxicosis >6 weeks, obtain endocrine consultation for additional workup 4
• Once euthyroid, monitor every 6-12 months 8

PCOS Management Considerations

Defer aggressive PCOS treatment until hyperthyroidism is controlled, as thyroid dysfunction can exacerbate metabolic and cardiovascular complications. Hyperthyroidism causes increased cardiac output, tachycardia, and altered metabolism that can confound PCOS symptom assessment 4, 5.

• Once thyroid function normalizes, resume standard PCOS management including lifestyle modification, metformin for insulin resistance, and hormonal contraceptives for menstrual regulation
• The presence of hyperthyroidism does not exclude other metabolic conditions, and both require attention 4

Critical Pitfalls to Avoid

• Never start thyroid hormone replacement if concurrent adrenal insufficiency is suspected, as this can precipitate adrenal crisis 8
• Do not use radioactive iodine in pregnancy or lactation, and avoid pregnancy for 4 months after administration 6
• Ensure patients are euthyroid before surgery using antithyroid medications and beta-blockers to prevent thyroid storm 5
• Monitor for thyroid storm, a rare but life-threatening complication requiring hospitalization, endocrine consultation, and aggressive treatment with beta-blockers, hydration, steroids, SSKI, or thionamides 4, 5
• Recognize that cardiovascular complications are the chief cause of death in hyperthyroidism, particularly in patients >50 years 4

Special Populations

For pregnant patients with hyperthyroidism, surgery is preferred over radioactive iodine, and antithyroid drugs should be used cautiously with close monitoring 5. Untreated hyperthyroidism causes adverse pregnancy outcomes 3.

For elderly patients or those with cardiac disease, the increased workload from hyperthyroidism can precipitate heart failure even with underlying structural heart disease 4. Aggressive beta-blockade and rapid thyroid control are essential 4, 5.