Endocrine Abstracts

There is a relative lack of data regarding the timing and in particular the severity of hypothyroidism post Radioiodine (RI). We retrospectively examined the timing and severity of hypothyroidism following RI in 213 patients, in relation to ‘target’ and actual follow up appointments, and the introduction of a nurse-led follow-up clinic. Hypothyroidism was defined as persistent elevation of TSH – mild (TSH 6.1–10 mU/l), moderate (TSH 10.1–50 mU/l) and severe (TSH > 50 mU/l). The target intervals between RI and subsequent first six outpatient visits were defined as; 6, 6, 8, 10, 12 and 16 weeks respectively. In the 178 patients who required only a single dose of RI (mean 479 MBq), 99 (56%) patients developed hypothyroidism. The timing of first detection of TSH elevation was; 14% patients at <8 weeks, 47% at 8 to <16 weeks, 24% at 16 to <24 weeks, 11% at 24 to <36 weeks, 1% at 36 to <52 weeks and 2% at >52 weeks. Two hundred and two patients had follow-up after one or more doses of RI and 120 (59%) patients developed hypothyroidism. Of these 120 patients, 14%, 44% and 42% developed mild, moderate or severe hypothyroidism respectively at first detection of hypothyroidism. In 54% of the patient visits the actual follow up visits were delayed beyond the targets. There was no difference between the physician-led and nurse-led clinics. Our experience suggests that the majority of patients develop hypothyroidism in the first six months post RI therapy. The severity of hypothyroidism when first detected is of concern and suggests that closer monitoring of thyroid function is required post RI. In view of outpatient cancellations and postponements, we are considering extending our nurse-led clinic to include additional thyroid function checks with interim telephone contact on a monthly basis for the first six months post RI.