Endocrine Abstracts

Growth hormone (GH) is thought to have a dual effect (direct and indirect) on bone metabolism. We sought to explore the inter-relationships and potential determinant factors of several markers of bone turnover in GH deficient adults (GHD), as well as possible acute changes arising from GH.

24 GHD subjects [14 M, 10F; age (range, 24-74 yrs)] were studied after consent and ethical approval. They were randomised into three groups (GP) of 8 subjects, each to receive a single intravenous (IV) GH (mg per kg body weight) injection of 0.0036 (GP1), 0.0071 (GP2) or 0.0143 (GP3). 6 of the subjects also received IV normal saline (Placebo) on a separate occasion. Fasting morning blood [for bone specific alkaline phosphatase (bALP), osteocalcin (OS), type I procollagen (PICP) and C-terminal telopeptide of type-I collagen (CTx)] and urine [cross-linked N-telopeptide (NTx)] were obtained before and 1, 2, and 3 days post injection.

Significant inter-correlations existed between baseline levels of all bone markers (Spearman's; P=0.01 or less). Age was a significant negative correlate with all markers (P=0.03 or less). Surrogate variables for GH status [insulin-like growth factor 1(IGF-1), IGF binding protein-3 (IGFBP-3), and BMI] were not significant determinants of any of the measured bone markers (multiple linear regression).

Changes from baseline were maximal on day 3. Expressed as percentages (median for GP1, GP2, GP3 and placebo, respectively), changes were as follows: for OS (9.0, 10.7, 13.3 and 6.2); PICP (14.3, 2.1, 5.7 and -0.9); CTx (-14.0, 30.5, 3.0 and 10.0); NTx (7.4, 25.6, -13.4 and minus 11.3) and bALP (0.5, -2.5, -0.1 and 5.0). Changes after the 3 GH doses were not significantly different from those after placebo.

Considerable day-to-day variability exists in bone turnover markers. No significant changes could be attributed to the administered intravenous growth hormone. The studied bone markers are significantly inter-correlated.