Increase in bone density and plasma osteocalcin during growth hormone therapy in growth hormone deficient children

Growth hormone: health considerations beyond height gain

The therapeutic benefit of growth hormone (GH) therapy in improving height in short children is widely recognized; however, GH therapy is associated with other metabolic actions that may be of benefit in these children. Beneficial effects of GH on body composition have been documented in several different patient populations as well as improvements in lipid profile. Marked augmentation of bone mineral density also seems evident in many pediatric populations. Some of these benefits may require continued therapy past the acquisition of adult height. With long-term therapy of any kind, the adverse consequences of treatment should also be considered. Fortunately, long-term GH treatment seems to be safe and well-tolerated. This review describes the long-term metabolic effects of GH treatment in the pediatric population and considers how these may benefit children who are treated with GH.

Long-term effects of growth hormone (GH) on bone mineral status and bone turnover markers in patients with isolated GH deficiency and multiple pituitary hormone deficiency

OBJECTIVE

This study was designed to assess the long-term effects of growth hormone (GH) replacement therapy on bone mass and bone turnover markers in children with isolated GH deficiency (IGHD) and multiple pituitary hormone deficiency (MPHD).

MATERIALS AND METHODS

Fifty children (35 IGHD, 15 MPHD) receiving GH replacement therapy were enrolled in the study. The patients were followed for 38.6 +/- 15.7 months (1-5 years). Bone mineral density (BMD) of the lumbar region and bone turnover markers [PTH, osteocalcin, bone-specific alkaline phosphatase (boneALP), and the carboxyterminal propeptide of type-1 collagen (CPP-I)] were assessed annually.

RESULTS

The height standard deviation score (SDS) of patients with IGHD and MPHD at diagnosis was statistically significant (P = 0.012), and the change in height SDS during 3 years (Deltaheight SDS(3 years)) was statistically similar between these two groups (P = 0.651). The BMD z-scores of the two groups were comparable at the start of GH therapy (P = 0.083), and then increased in both groups similarly during 5 years of GH replacement therapy (F = 0.349, P = 0.567). When the BMD z-scores during 5 years of GH therapy were analysed in the IGHD and MPHD groups separately, it was found that the BMD z-score increased significantly in IGHD (P < 0.001) but the increase was not significant in MPHD (P = 0.140). Multiple regression analysis showed that the change in BMD z-score during 3 years of GH therapy (DeltaBMD z-score(3 years)) was predicted by the BMD z-score and height SDS at the start of GH therapy and by Deltaheight SDS(3 years) in the IGHD group (t = -2.582, P = 0.02; t = 2.322, P = 0.034 and t = 2.908, P = 0.01, respectively). Age and BMD z-score and height SDS at diagnosis were found to have predictive values for the DeltaBMD z-score(3 years) (t = -3.652, P = 0.022; t = -4.073, P = 0.015 and t = 3.389, P = 0.028, respectively) in the MPHD group. The changes in boneALP, osteocalcin, CPP-1 and PTH levels during the therapy were statistically similar between the IGHD and MPHD groups.

CONCLUSION

BMD increased during GH therapy in the IGHD and MPHD groups. GH had a positive effect on bone mass in the short as well as the long term. Early diagnosis and treatment could improve peak bone mass in patients with MPHD. The time and dose of sex steroids for pubertal induction and progression, which mimics physiological secretion, might also contribute to bone accretion in patients with MPHD.

Responses of bone turnover markers and bone mineral density to growth hormone therapy in children with isolated growth hormone deficiency and multiple pituitary hormone deficiencies

Growth hormone deficiency (GHD) is an important cause of decreased bone mass in childhood and adolescence. The role of other pituitary hormone deficiencies on bone mass is still a query in children. Thirty-nine children (28 with isolated GHD [IGHD] and 11 with multiple pituitary hormone deficiency [MPHD]) were investigated to show the effects of IGHD vs MPHD on bone status. Bone turnover markers (calcium, phosphate, alkaline phosphatase [ALP] Bone ALP [BALP], osteocalcin [OSC], carboxyterminal propeptide of type-1 collagen [CPP-I], parathyroid hormone [PTH]) were measured before and every four months during growth hormone (GH) therapy; bone mineral density (BMD) of the lumbar spine was measured before and every six months during therapy. All bone turnover markers except calcium and PTH increased significantly during 1 year of GH therapy. There were no differences in the levels of bone turnover markers between children with IGHD and MPHD at baseline, and after 4, 8 and 12 months of therapy. Lumbar spine BMD SDS of all patients increased significantly during 1 year of therapy (p = 0.035 after 6 months and p <0.001 after 12 months compared with baseline). BMD SDS of both IGHD and MPHD groups were similar at baseline and after 6 and 12 months of therapy (p = 0.235, p = 0.295 and p = 0.384). Height SDS (HtSDS) at baseline was the most important predictor of baseline BMD SDS in children with GHD (t = 4.166, p <0.001). DeltaHtSDS was also positively related to deltaBMD SDS after 1 year of GH therapy. In conclusion, there was no difference in bone status of the patients with IGHD and MPHD at baseline. GH therapy yielded similar increases in bone mass in both groups. Increase in height contributed to increase in BMD during 1 year of GH therapy.

Measurement of volumetric bone mineral density accurately determines degree of lumbar undermineralization in children with growth hormone deficiency

The effect of anthropometric variables and bone size on bone mineral density (BMD) was examined in 22 children with GH deficiency (GHD) aged 6.1-8.0 yr at diagnosis and in 40 sex- and chronological age-matched controls. In all patients and controls, bone mineral content (BMC), BMDarea and BMD corrected for the apparent bone volume (BMDvolume) were measured by dual-energy x-ray absorptiometry in the lumbar spine at L2-L4 level. In patients, BMDarea was corrected for body height (BMDheight), body mass index (BMDBMI), and bone age (BMDBA). Patients showed significantly reduced (P < 0.0001) BMC (males 11.55 +/- 0.71 g, females 10.13 +/- 1.48 g) and BMDarea (males 0.502 +/- 0.033 g/cm2, females 0.515 +/- 0.034 g/cm2) compared with controls (BMC: males 18.09 +/- 1.23 g, females 15.58 +/- 1.87 g; BMDarea: males 0.689 +/- 0.065 g/cm2, females 0.685 +/- 0.059 g/cm2). In patients, BMDheight (males 0.537 +/- 0.031 g/cm2, females 0.548 +/- 0.032 g/cm2) and BMDBMI (males 0.641 +/- 0.028 g/cm2, females 0.624 +/- 0.035 g/cm2) remained significantly lower (P < 0.02 to P < 0.0001) than BMDarea of controls. BMDBA of patients was significantly reduced (-1.49 +/- 0.51 Z score, P < 0.0001) in comparison with bone age-matched controls (n = 35). BMDvolume was significantly lower (P < 0.01 to P < 0.0005) in patients (males 0.268 +/- 0.006 g/cm3, females 0.276 +/- 0.010 g/cm3) compared with chronological age-matched controls (males 0.283 +/- 0.013 g/cm3, females 0.293 +/- 0.017 g/cm3). Mean bone volume of patients was affected to a greater extent than bone area (-2.36 +/- 0.49 Z score and -1.56 +/- 0.70 Z score, respectively). Bone area/bone volume ratio was significantly higher in patients than in chronological age-matched controls (0.53 +/- 0.02 and 0.42 +/- 0.08, P < 0.0001, respectively). Chronological age, body height, BMI, and bone age correlated significantly with BMDarea (r2 = 0.389-0.450, P < 0.002 to P < 0.001) but not with BMDvolume (P = not significant). The results show that anthropometric variables and bone size affect lumbar BMC and BMDarea in children with GHD. Reduced lumbar BMDvolume indicates that apparent true bone density is decreased in children with GHD, suggesting a role of GH in bone mineralization.