ESPE Abstracts

Objective and hypotheses: The purpose was to get the basic data of optimum serum concentration of estrogen in maximizing pubertal growth spurt, and decreasing the acceleration of epiphyseal closure of long bones.

Method: i) Fifteen female SD rats (13-week aged; post pubertal growth spurt) were randomly divided into three groups. After 1 week, the group 1 were injected subcutaneously with sesame oil, as a control, group 2 were with 10 μg/kg per week of estradiol depo as a low-dose, and group 3 were with 100 μg/kg per week of it as a high-dose for 8 weeks on their posterior neck area. ii) Their crown-lump length, body weight were checked weekly. iii) Serum levels of GH and estradiol were checked with ELISA before and after injections. iv) After 8 weeks of injections, they were euthanized, their proximal tibias and distal femurs were dissected and stained with hematoxylin-eosin. v) The thicknesses of epiphyseal plate including proliferative and hypertrophic zone of the proximal tibias and distal femurs were measured in 20 evenly divided sites with microscope. vi) Statistical analyses were done among the three groups before and after injections using ANOVA with multiple comparisons for auxological data, and Kruskall–Wallis test for seum levels of GH, estradiol levels with SPSS ver.21.0.

Results: i) There were no significant differences in body lengths and body weights among 3 groups. ii) Serum GH levels were significantly increased in both group 2 and group 3. iii) There is a tendency that epiphyseal plate thicknesses were decreased with high dosage of estrogen, but it is not statistically significant.

Conclusion: i) Both low and high dose estrogen could increase the secretion of GH. ii) There is a tendency that epiphyseal plate thickness had a negative relation with estrogen dosage, but larger sample studies are needed iii) The effects of estrogen on epiphyseal plate in rodents may be different with human, therefore this kind of studies in animal models other than rodents are necessary.