Abstract
To evaluate the role of GH in the growth retardation of HT, 7-weeks-old female rats were rendered HT by methimazol for 7 weeks (Grl). This resulted in serum T4<1μg/dl (ctr 2.4±0.4 μg/dl), growth arrest and 96% depletion of pituitary contents of GH (from 78±3 to 3±3 μg/pit). Supplementation with L-thyroxine (T4) for the last 2 weeks (Gr2) restored pituitary GH to 23±4 μg/pit and accelerated rats' growth from -3 g/wk to +9 g/wks. Treatment of HT rats with hGH for the last 2 weeks (wks 12-14 of life) (Gr3) resulted in intermediate growth of +3 g/wks. Combined treatment with T4 and hGH (Gr4) increased growth further to 12g, wk. The proximal tibiae were dissected and the epiphysis, metaphysis and growth plate were evaluated qualitatively and measured morphometrically. In the control group (ctr) the metaphyseal trabecular bone was 54±2% of the total bone. In Grs 1-4 it was 18±2, 36±3, 24±2 and 34±2% respectively. The epiphyseal trabecular bone in ctr and Grs 1-4 was 43±3, 30±2, 46±2, 41±2 and 36±2% resp. The width of the compact tibial midshaft was 597±21, 373±14, 432±19, 330±16 and 453±4 microns resp. The width of the epiphyseal growth plate was 189±6, 140±3, 262±14, 126±5 and 300±9 microns resp. While the HT plate was noted for more resting cells, less and smaller proliferating cell and arrest of cartilage remodelling into metaphyseal bone hGH replacement resulted in only minor improvement and T4 replacement enhanced proliferation and remodelling. Combined treatment resulted in further increase of proliferation. It is concluded that GH-deficiency is responsible for only a small part of the epiphyseal cartilage and bone changes of HT, and that GH requires thyroid hormones for its full expression.
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Hochberg, Z., Lewinson, D., Harel, Z. et al. 85 THE IMPORTANCE OF GRWOTH HORMONE (GH) IN THE EPIPHYSEAL CARTILAGE AND BONE CHANGES OF HYOTHYROIDISM (HT). Pediatr Res 24, 531 (1988). https://doi.org/10.1203/00006450-198810000-00106
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DOI: https://doi.org/10.1203/00006450-198810000-00106