Background: Following the advent of thyroid function screening and highly sensitive TSH assay subclinical hyperthyroidism (SCHT) is becoming increasingly common. No audit addressed the treatment outcome of this group of patients.
Methods: Prospective analysis of management outcome of patients seen in endocrine clinic over 36 months was carried out. 46 patients who presented with SCHT were included, of whom 41 had confirmed SCHT on repeat testing.
Results: 41 patients (92.7% female) mean age 64 years, range 2785, presented with SCHT due to either multinodular enlargement (70.7%), toxic nodule (9.8%), autoimmune (7.3%). 51.2% of patients were symptomatic, 39% patients either had bone or heart disease. Majority of patients (n=33, 80.5%) consented and thus were treated with 400 MBq of radioiodine, others preferred to be kept under observation (n=5, 12.2%), one patients was treated with anti-thyroid medications, one just received radioiodine and one was lost to follow up.
Of those who were treated with radioiodine, 31 patients whose outcome at 3 and or 6 months was known were selected. All but one were postmenopausal women, 58.1% patients were symptomatic, 32% had fully suppressed TSH, 41.9% had either bone or heart disease, and most of them (n=23, 74.2%) had multinodular enlargement. After 3 months of receiving radioiodine, 16.1% patients still remained subclinically hyperthyroid, 58% patients became euthyroid and 6.5% patients became hypothyroid. After 6 months of receiving radioiodine, 3.2% patients remained subclinically hyperthyroid, 77.4% patients became euthyroid, 6.5% became hypothyroid, and one patient became hyperthyroid. 80% of patients with TSH fully suppressed at diagnosis, who were treated with RAI, were cured at the end of 6 months.
Conclusion: Radioiodine treatment is acceptable and effective treatment to most of patients with SCHT with low failure rate. These results are comparable with treatment of overt thyrotoxicosis. The long term clinical benefits remain to be studied.