Abstract
Objective: to evaluate metabolism of vitamin D and calcium-phosphorus metabolism in patients with an active phase of acromegaly in comparison with healthy individuals. Materials and Methods: The study included 44 patients with an active acromegaly (IGF-1 788 [521; 963] ng/mL), as well as 49 conditionally healthy individuals. There were more men in the Acromegaly group (41% vs. 20%, p <0.05), patients were older (median age 42.7 [35.5; 26.5] vs. 26.3 [25; 33.5] years, p <0.05) and had a higher BMI (28.4 [25.2; 30.2] vs. 22.2 [20.1; 26.1] kg/m2, p <0.05) in a minor way compared with the control group. All participants were tested for vitamin D metabolites (25(OH)D3, 25(OH)D2, 1,25(OH)2D3, 3-epi-25(OH)D3 and 24,25(OH)2D3) by UPLC-MS/MS, free 25(OH)D and vitamin D-binding protein by ELISA, PTH by electrochemiluminescence immunoassay, as well as routine biochemical parameters of blood serum (calcium, phosphorus, creatinine, albumin, magnesium) and urine (calcium and phosphorus-creatinine ratio in spot urine). Results: In the Acromegaly group, we observed significantly higher levels of serum total calcium (2.46 [2.37; 2.56] vs. 2.38 [2.33; 2.45] mmol/L, p <0.05), albumin-corrected calcium (2.33 [2.28; 2.42] vs. 2.26 [2.21; 2.31] mmol/L, p <0.05) and phosphorus (1.39 [1.25; 1.55] vs. 1.15 [1.06; 1.23] mmol/L, p <0.05) as well as lower levels of serum albumin (45 [44; 47] vs. 46 [45; 48] g/L, p <0.05). The rest of the studied biochemical parameters and PTH levels did not differ significantly between the groups. The IGF-1 level in patients with acromegaly positively correlated with the level of total calcium (r = 0.49, p <0.05), albumin-corrected calcium (r = 0.49, p <0.05) and phosphorus (r = 0.55, p <0.05). The Acromegaly group showed lower levels of 25(OH)D3 (14.8 [11.8; 20.5] vs. 20.5 [14.8; 24.6] ng/mL, p <0.05), 3-epi-25(OH)D3 (1.0 [0.7; 1.4] vs. 1.4 [0.9; 1.8] ng/mL, p <0.05), 24,25(OH)2D3 (0.8 [0.4; 1.2] vs. 1.7 [0.9; 2.6] ng/ml, p <0.05) and free 25(OH)D (4.6 [3.7; 5.6] vs. 5.9 [4.0; 7.5] pg/mL, p <0.05), higher levels of 1,25(OH)2D3 (50 [42; 63] vs. 39 [34; 45] pg/mL, p <0.05), a lower 25(OH)D3/1,25(OH)2D3 ratio (289 [226; 443] vs. 517 [340; 641], p <0.05) and a higher 25(OH)D3/24,25(OH)2D3 ratio (19.3 [15.4; 27.7] vs. 11.9 [9.6; 15.2], p <0.05). Conclusion: Our data suggest that high levels of the active vitamin D metabolite (1,25(OH)2D3) resulting from an increase in 1α-hydroxylase activity may contribute to the elevation of calcium and phosphorus serum levels in patients with acromegaly. Our results also indicate a decrease in 24-hydroxylase activity in patients with acromegaly, which may be due to lower levels of 25(OH)D3 in these patients. The results obtained should be evaluated taking into account the observed differences in age, gender and BMI between groups.