Characteristics of Non-Renal Normocalciemic Hyperparathyroidism in the Chornobyl NPP Accident Survivors

Abstract

Objective: to assess the hormonal and metabolic disorders in the Chernobyl nuclear power plant (ChNPP) accident survivors (AS), having got secondary normocalcemic non-renal hyperparathyroidism (HPT) in the late period upon exposure to ionizing radiation (IR). Materials and methods. The routine clinical, anthropometric, instrumental (thyroid and parathyroid diagnostic ultrasound), laboratory (biochemical, hormonal), statistical methods were applied. In both prospective (n = 48, control group n = 19) and retrospective studies the data of 2,234 subjects including 1,372 irradiated adults (862 nonirradiated persons in the control group) were evaluated. Clinical consequences of exposure to IR on the endocrine system were evaluated in ChNPP AS. Results. High prevalence of vitamin D lack or deficiency was established retrospectively in 81.8 % of the ChNPP AS and in 89.5 % of the control group subjects. In general, there was neither effect of exposure to IR on the vitamin D status in study subjects, nor any difference between the study groups. According to diagnostic ultrasound patterns the parathyroid hyperplasia was diagnosed in 629 cases (28.2 %). Among the ChNPP AS it was found in 32.7 % of cases (n = 450) vs. 20.7 % (p > 0.005) in the control group (a 1.6-fold difference). HPT diagnosed as serum parathyroid hormone content > 65 ng/ml was diagnosed in 123 cases (21.1 %) i.e. in almost every fifth person. Increased serum level of parathyroid hormone was found in the 94 ChNPP AS and in 25 persons of the comparison group. In other words, the frequency of HPT was 23.7 % among the AS being significantly more than in the comparison group (13.2 %, p < 0.005). Frequency of normocalcemic non-renal HPT was slightly different by years of observation with a trend to the year-by-year increase. Conclusions. High prevalence of vitamin D lack or deficiency was established in the ChNPP AS, being however independent of exposure to IR. Frequency of parathyroid hyperplasia/adenoma was 1.6 times higher in the irradiated subjects than in persons of the control group. Annual increase in frequency of the non-renal normocalcemic HPT was also revealed reaching nowadays 23.7 % among the AS, which is significantly higher than in the comparison group. Key words: Chornobyl nuclear power plant accident, ionizing radiation, exposure to ionizing radiation, accident survivors, participants of the accident consequences clean-up, parathyroids, hyperplasia, hyperparathyroidism, thyroid.