How to decide on discontinuation of Neomercazole (Carbimazole) in a 52-year-old euthyroid female with a history of biochemical hyperthyroidism, currently on a low dose of 5mg every alternate day, with normal Thyroid-Stimulating Hormone (TSH) and Thyroid Peroxidase (TPO) levels, no goitre, and stable vital signs?

Discontinuation of Neomercazole (Carbimazole) in Biochemical Hyperthyroidism

Discontinue carbimazole now and monitor TSH every 6-8 weeks for the next 6 months, as this patient demonstrates clear biochemical and clinical remission after adequate treatment duration.

Evidence Supporting Discontinuation

This patient meets all criteria for attempting drug withdrawal:

• Treatment duration is adequate - She has been on antithyroid drugs for "few years" which exceeds the standard 12-18 month treatment course recommended for Graves' disease 1
• Currently euthyroid - Normal TSH indicates restoration of thyroid-pituitary axis function, which is the primary goal of antithyroid drug therapy 1
• Minimal dose requirement - The reduction to 5mg alternate day (equivalent to 2.5mg daily) suggests minimal residual disease activity 2
• Normal TPO antibodies - Absence of positive thyroid antibodies reduces relapse risk, though this is not an absolute predictor 3
• No goiter - Absence of goiter is associated with better outcomes and shorter treatment duration 2

Discontinuation Protocol

Immediate steps:

• Stop carbimazole completely today - there is no need for gradual tapering at this minimal dose 2
• Recheck TSH and free T4 in 6-8 weeks to confirm sustained euthyroidism 1
• Continue monitoring TSH every 6-8 weeks for the first 6 months, then every 3-6 months for the next year 3

Critical monitoring parameters:

• TSH suppression (<0.10 mU/L) during follow-up indicates subclinical hyperthyroidism and significantly higher relapse risk (P<0.02) 3
• Clinical symptoms of hyperthyroidism (tremor, palpitations, weight loss, heat intolerance) warrant immediate TSH and free T4 measurement 1
• Measure free T4 and free T3 if TSH becomes suppressed, as normal TSH with suppressed free hormones can occur in early relapse 3

Expected Outcomes and Relapse Risk

Realistic expectations:

• Approximately 50% of patients relapse after carbimazole discontinuation, typically within the first year 1
• Relapse rate is 39% in patients treated with short-term carbimazole (median 18 weeks), suggesting longer treatment may improve outcomes 2
• Patients with suppressed TSH during clinical remission have significantly higher relapse risk compared to those with normal TSH 3

Factors favoring sustained remission in this patient:

• Long treatment duration (several years vs. standard 12-18 months) 1
• Absence of goiter 2
• Normal TPO antibodies 3
• Very low dose requirement (5mg alternate day) suggesting minimal disease activity 2

Management of Potential Relapse

If relapse occurs (elevated free T4/T3 with suppressed TSH):

• Restart carbimazole at 15-30mg daily, not the previous minimal dose 1, 2
• Consider definitive therapy (radioiodine or thyroidectomy) as second-line treatment, since relapse after adequate medical therapy indicates lower likelihood of sustained remission with repeat drug therapy 1
• Radioiodine is particularly appropriate for this 52-year-old woman who is presumably past childbearing age 1

Critical Pitfalls to Avoid

• Do not continue carbimazole indefinitely - There is no evidence that prolonged treatment beyond achieving euthyroidism improves long-term remission rates, and it exposes the patient to unnecessary medication side effects 1
• Do not stop monitoring after discontinuation - Most relapses occur within the first year, requiring vigilant TSH surveillance 3
• Do not ignore suppressed TSH with normal free hormones - This represents subclinical hyperthyroidism and predicts imminent relapse (P<0.02) 3
• Do not restart at minimal dose if relapse occurs - Full therapeutic doses (15-30mg daily) are required to regain control 1, 2

Special Considerations

Why this patient is an ideal candidate for discontinuation:

• The absence of positive TSH-receptor antibodies (implied by "no other antibody profile") and normal TPO reduces but does not eliminate relapse risk 3
• Her stable vital signs and heart rate confirm absence of subclinical hyperthyroidism 1
• Normal liver function and blood counts confirm no drug toxicity requiring continuation for safety monitoring 1

Alternative approach if concerned about relapse:

• Some clinicians prefer confirming normal TSH response to TRH stimulation before discontinuation, though this is not standard practice 2
• However, given her long treatment duration and minimal dose requirement, proceeding with discontinuation and close monitoring is more practical than additional testing 2