The effect of prolactin itself and in combination with estrogen on bone mineral density in female rats

New concepts in regulation and function of the FGF23

In comparison to the regulation of calcium homeostasis, which has been widely studied over the last several decades, phosphate homeostasis is little understood. The parathyroid hormone (PTH)/vitamin D axis has traditionally been used as a conceptual framework for understanding mineral metabolism. Recently, the fundamental regulator of phosphate homeostasis, fibroblast growth factor 23 (FGF23), which is produced by osteocytes and is involved in the hormonal bone-parathyroid-kidney axis, has attracted more attention. The secretion of FGF23 is controlled by diet, serum phosphate levels, PTH, and 1,25(OH)2 vitamin D. FGF-23, the FGF receptors and the obligate co-receptor α-Klotho work in concert to affect FGF-23 actions on targeted organs. Despite all efforts to investigate pleotropic effects of FGF23 in various endocrine organs, many aspects of the regulation and functions of FGF23 and the exact crosstalk among FGF23, serum phosphate, calcium, PTH, and vitamin D in the regulation of mineral homeostasis remain unclear; much efforts need to be established before it can be moved toward therapeutic applications. In this regard, we provide a brief overview of the novel findings in the regulation and function of FGF23 and refer to related questions and hypotheses not answered yet, which can be a window for future projects. We also focus on the current knowledge about the role of FGF23 obtained from our researches in recent years.

Prolactin is associated with bone mineral density in subjects with type 2 diabetes mellitus

PURPOSE

Prolactin (PRL) exerts actions in the bone besides lactation and reproduction. This study aimed to investigate whether PRL is related to bone mineral density (BMD) in type 2 diabetes mellitus (T2DM).

METHODS

A total of 642 patients with T2DM were divided into two groups with age and body mass index (BMI) matched: mildly increased PRL (HP group, n = 101) or normal PRL (NP group, n = 541). BMD was measured by dual-energy X-ray absorptiometry and compared.

RESULTS

1) BMD, T score at lumbar spine L1-4, right hip and femur neck, and Z score at the femur neck were significantly higher in the HP than in the NP group (0.96 ± 0.16 vs. 0.92 ± 0.15g/cm², p = 0.019; 0.88 ± 0.15vs. 0.84 ± 0.14 g/cm², p = 0.007; 0.75 ± 0.17 vs.0.70 ± 0.13 g/cm², p = 0.001; -0.90 (-1.85, -0.20) vs. -1.40 (-2.20, -0.40), p = 0.018; -0.80 (-1.50, -0.30) vs. -1.10 (-1.80, -0.53), p = 0.026; -1.30 (-2.00, -0.60) vs. -1.70 (-2.20, -1.00), p = 0.001; -0.20 (-0.70, 0.30) vs. -0.40 (-0.90, 0.10), p = 0.026). In men, T and Z scores at the right hip and femur neck were significantly higher in the HP than in the NP group (-0.70 (-1.32, 0.20) vs. -0.90 (-1.50, -0.40), p = 0.038; -0.20 (-0.80, 0.20) vs. -0.50 (-0.10, 0.10), p = 0.027; -0.30 (-0.60, -0.30) vs. -0.40 (-0.90, 0.20), p = 0.038) but not in women. Bone turnover markers have no significant difference between groups (all p > 0.05). 2) BMD at the right hip and Z score at the right hip and femur neck were significantly positively associated with PRL (r = 0.087, p = 0.029; r = 0.089, p = 0.024; r = 0.087, p = 0.029). In men, BMD at L1-4 and the right hip; T score at L1-4, the right hip, and the femur neck; and Z score at the right hip and the femur neck were significantly positively associated with PRL (r = 0.122, p = 0.007; r = 0.105, p = 0.041; r = 0.123, p = 0.016; r = 0.110, p = 0.032; r = 0.115, p = 0.025; r = 0.121, p = 0.018; r = 0.138, p = 0.007) but not significant in women. 3) In men divided into two groups according to T score (T score at the right hip>-1 or T score at the right hip≤-1) or the median BMD at L1-4, the right hip or the femur neck, PRL was significantly higher in the higher BMD than in the lower BMD group (16.32 ± 6.12 vs. 14.78 ± 5.68 ng/ml, p = 0.012; 16.20 ± 6.21 vs. 14.73 ± 5.40 ng/ml, p = 0.014; 16.10 ± 6.01 vs. 14.80 ± 5.77 ng/ml, p = 0.032; 16.17 ± 6.04 vs. 14.76 ± 5.77 ng/ml, p = 0.02; 16.48 ± 6.05 vs. 14.98 ± 5.81 ng/ml, p = 0.020; 16.10 ± 5.98 vs. 14.80 ± 5.87 ng/ml, p = 0.035).

CONCLUSION

Increased PRL was associated with better BMD in patients with T2DM, especially in men. PRL within the biologically normal range may play a protective role in the BMD of T2DM.