Prüfung einer potentiellen strahleninduzierten Nebenschilddrüsenfunktionsstörung während einer Radioiodtherapie benigner Schilddrüsenerkrankungen

The intention of the present thesis was the evaluation of a potential parathyroid dysfunction under treatment with radioactive iodine of benign thyroid diseases. It was to be examined whether a change in the parathyroid function would arise within the first week on treatment. At the department of nuclear medicine of the university hospital Gießen-Marburg GmbH, location Marburg, a prospective cohort study was executed on radioactive iodine therapy of benign thyroid diseases with 105 probands (75 women / 30 men, mean age 60.62 ± 14.3 years). According to their thyroid diseases these 105 probands were classified into following subgroups: thyroid adenoma with 23 patients, multifocal thyroid autonomy with 8 patients, disseminated thyroid autonomy with 37 patients as well as the subgroup Graves’ hyperthyroidism (without Graves’ ophtalmopathy) and accordingly Graves’ disease (with Graves’ ophtalmopathy) with 37 patients. The serum level of the intact parathyroid hormone was determined directly before starting the radioactive iodine therapy on the admission day and on day 1, 3 and 5 of the radioactive iodine therapy as well as at the ambulant follow-up examination one month after the start of the therapy. In case of 99 of 105 probands the serum level of parathyroid hormone declined on treatment with 131I with its nadir on day 3 of therapy (decline by 15.71 ng/l or 27.54%). The serum level of intact parathyroid hormone prior to radioactive iodine therapy was on average 48.99 ± 24.05 ng/l [n = 105], on day 1 after 131I administration it decreased to 34.09 ± 16.25 ng/l [n = 100], on day 3 to 32.74 ± 14.11 ng/l [n = 97], on day 5 to 37.02 ± 21.52 ng/l [n = 54] and at the follow-up examination one month after the start of the therapy it was on average 44.62 ± 20.54 ng/l [n = 91]. On average the patients received a mean activity of 1341.43 ± 459.16 MBq [n = 105] and the thyroid dose was on average 422.53 ± 245.56 Gy [n = 101]. The one-way analysis of variance of all data up to day 3 confirmed the decline in the serum level of parathyroid hormone (p < 0.0001). The student t-test for paired samples resulted in a statistically significant decrease in the mean values of parathyroid hormone level before therapy with regard to the mean values on day 1 (p < 0.0001) and on day 3 (p < 0.0001). The two-way analysis of variance, however, did not show a significant difference in the decline of the parathyroid hormone level with regard to the course of the four subgroups (p = 0.32). A correlation between the absolute or relative decline of the parathyroid hormone level and the thyroid dose could not be proved. The present thesis demonstrates for the first time that already within the first days of radioactive iodine therapy a decline in parathyroid serum level occurs most likely as consequence of an acute parathyroid dysfunction. The hypothesis was set up that the decreased parathyroid function under treatment with 131I is a consequence of the ionizing radiation.