Resumo

SAAVEDRA, MS et al. PTH Levels in Patients Treated with Bisphosphonates. Rev. argent. endocrinol. metab. [online]. 2012, vol.49, n.2. ISSN 1851-3034.

PTH reference intervals (RI) defined in subjects in which the causes of increased levels of PTH have not been fully excluded have been questioned; an optimal RI must coexist with adequate vitamin D levels. In this study we analyzed the RI in post-menopausal women with adequate levels of 25 (OH) D, treated with oral bisphosphonates. Because of their mechanism of action, bisphosphonates may produce an asymptomatic decrease of serum calcium and an increase in PTH; therefore, the 15-65 pg/ml RI reported for intact PTH molecule measurement by electrochemiluminescence may not be suitable for this particular population. The mean and standard deviation age of the subjects was 71.4±8.55 years; mean for 25 (OH) D3: 37.3 ng/ml; calcium ion: 4.9 mg/dl (RR 4.3-5.3); urinary calcium: 110 mg/24 hours (RR: 60-200); serum phosphorus: 3.6 mg% (RR: 2.5-4.5); urinary phosphorus: 0.61 g/24hs (RR:0.3-1.0); serum creatinine: 0.80 mg% (RR: 0.5-1.5) and eGFR of 74 min/ml/1.73m² (cut off > 60). BCTx for the average obtained was 212 pg/ml, reflecting the antirresorptive action of bisphosphonates. The RI calculated for PTH in this population, with the method recommended by the CLSI C28-A3, was 26.2 to 87.7 ng/ml. By multiple linear regression (r²= 0.14) of the dependent variable PTH with the predictors pCTx and creatinine, adjusted for age, PTH values depended on pCTx (P = - 0.024, p-value = 0.022) and creatinine (P = 22.294, p-value = 0.040). Our results demonstrate the increase in PTH levels would be due to the effect of antiresorptive therapy and the natural physiological aging process. Conclusion: The RI used for the general population would not be applicable to postmenopausal women with sufficient levels of 25OHD3, supplemented with calcium, treated with oral bisphosphonates. No financial conflicts of interest exist.

Palavras-chave : PTH; Bisphosphonates; Glomerular filtration; PCTx; Creatinine.

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