Correlation between longitudinal bone growth, growth hormone, and insulin-like growth factor-I in prepubertal dogs

Objective - To determine the association between longitudinal bone growth and concentrations of growth hormone (GH) and insulin-like growth factor-I (IGF-I) in serum from prepubertal dogs. Animals - 6 male 14-week-old German Shepherd Dogs. Procedure - Blood was obtained every 30 minutes for 14 consecutive days. Concentrations of GH and IGF-I in serum were determined, using a canine-specific radioimmunoassay and conventional radioimmunoassay after acid-ethanol extraction, respectively. Simultaneous biplanar radiography was performed daily to measure bone growth. Spectral analysis was used to estimate specific features of GH secretion during an extended period. Multiple linear regression with different lag times between independent and dependent variables was used to determine the strongest predictors of bone growth. Results - The power spectra of GH concentrations in serum had a primary peak at a frequency of 0.02 cycles/h or a periodicity of 50 h/cycle. A significant determinant of longitudinal bone growth was a lag time of 1 day in concentration of GH in serum. The relationship between IGF-I concentration in serum and bone growth was not significant. Conclusions - The primary frequency of GH secretion is outside the time frame of a single day and the concentration of GH in serum is a primary determinant of bone growth. Clinical Relevance - A better understanding of the components of bone growth provide discernment to improved diagnosis and treatment of abnormal bone growth.