Endocrine Abstracts

Background: Acromegaly is a rare disease, mostly caused by a GH (growth hormone)-secreting pituitary adenoma. The pathomechanism of bone complications remains not fully explored. The fibroblast growth factor-23 (FGF-23)/Klotho axis regulates phosphate and vitamin D metabolism.

Objectives: The study aimed primarily at evaluating FGF-23 and Klotho concentrations with regard to acromegaly activity. The secondary goal was to identify associations between FGF-23/Klotho axis and GH, IGF-1, calcium and phosphate metabolism parameters, and bone mineral density (BMD) measurements.

Methods: The study group comprised 67 patients with acromegaly and 50 controls (CG). Based on clinical presentation and hormonal evaluation (GH and IGF-1 concentrations) acromegaly group was divided into three subgroups: active acromegaly (AA); controlled disease (CD), and cured acromegaly (CA). We measured concentrations of the hormones and biochemical parameters. The lumbar spine (LS) and femoral neck (FN) BMD were assessed using dual-energy X-ray absorptiometry.

Results: The highest Klotho levels were found in the AA group and the lowest in the CG group (P=0.008). There were no statistically significant differences in FGF-23 concentrations among the subgroups of patients, despite of used classification. Similarly, we did not observe significant differences in age, sex, BMI, calcium, inorganic phosphate, alkaline phosphatase, 25(OH)D, creatinine, and BMD measurements. The patients with controlled disease had significantly higher PTH levels than in the AA and the CG group (P=0.011; P=0.001, respectively). FGF-23 correlated positively with alkaline phosphatase in the AA group (r=0.692, P=0.039) and with inorganic phosphate and age in the CA group (r=0.704, P<0.001; r=0.670, P<0.001; respectively). There was also a positive correlation between Klotho and IGF-1 in the AA group (r=0.733, P=0.025). Negative correlations between Klotho and LS T-score, LS BMD were observed in the CA group (r=−0.639, P=0.034; r=−0.745, P=0.009; respectively).

Conclusions: The FGF-23/Klotho system seems not to play a crucial role in bone metabolism in acromegaly patients.