Reversible primary hypothyroidism in Japanese patients undergoing maintenance hemodialysis

BACKGROUND/METHODS: The presence or absence of hypothyroidism was assessed in 152 consecutive Japanese patients with end-stage renal disease on hemodialysis. Eight patients who had undergone treatment for thyroid disease before starting hemodialysis therapy, and 3 patients with amyloidosis due to rheumatoid arthritis were excluded. RESULTS: Of the remaining 141 hemodialysis patients, 14 (9.9%) (9 males and 5 females, aged 69.1 A+/- 8.8 years with a mean duration of hemodialysis of 69 A+/- 51 months) were in a hypothyroid state, defined as a thyroid-stimulating hormone (TSH) level > 5 mU/l. Antithyroid peroxidase antibodies were positive in only 1 of the 14 patients, while antithyroglobulin antibodies were negative in all of these patients. After iodide restriction, the serum TSH level decreased in all the patients from a mean of 16.49 A+/- 22.80 to 4.44 A+/- 3.35 mU/l after 1 month, 4.25 A+/- 2.24 mU/l after 2 months and 3.97 A+/- 2.22 mU/l after 3 months. The 3 months of iodide restriction were also associated with decreases in systolic blood pressure (142 A+/- 19 to 125 A+/- 16 mmHg, p < 0.05), diastolic blood pressure (79 A+/- 13 to 72 A+/- 9 mmHg, p < 0.05) and thyroid gland volume estimated by ultrasonography (13.7 A+/- 6.3 to 11.6 A+/- 5.2 ml, p < 0.05). CONCLUSION: A high prevalence of reversible primary hypothyroidism was found in end-stage renal disease patients on hemodialysis. Retention of excess iodide may be the mechanism responsible for reversible hypothyroidism rather than immunological perturbations. It is, therefore, recommended to attempt iodide restriction before starting l-thyroxine replacement therapy.