Correlation between longitudinal bone growth, growth hormone, and insulin-like growth factor-1 in prepubertal dogs

Objective-To determine the association between longitudinal bone growth and concentrations of growth hormone (GH) and insulin-like growth factor-I (IG F-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. Conc entrations of GH and IGF-I in serum were determined, using a canine-specifi c radioimmunoassay and conventional radioimmunoassay after acid-ethanol ext raction, respectively. Simultaneous biplanar radiography was performed dail y to measure bone growth. Spectral analysis was used to estimate specific f eatures of GH secretion during an extended period. Multiple linear regressi on 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 significa nt determinant of longitudinal bone growth was a lag time of 1 day in conce ntration of GH in serum. The relationship between IGF-I concentration in se rum 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 determin ant of bone growth. Clinical Relevance-A better understanding of the components of bone growth provide discernment to improved diagnosis and treatment of abnormal bone gr owth.