LONG-TERM HYPOTHYROIDISM CAUSES DECREASED BONE COMPETENCE IN MALE EUROPEAN STARLINGS, STURNUS-VULGARIS

Male European starlings were thyroidectomised and held on either short or long day photoperiods. Intact euthyroid control birds were also he ld on either short or long days to control for differences in reproduc tive condition. Femora of birds from each group were sampled following plasma thyroxine measurement. Hypothyroidism caused decreased bone me chanical competence in starlings, as determined by Vickers microhardne ss testing. It was also found that transfer from short to long dayleng ths caused increased plasma thyroxine concentration, but that this did not affect bone mechanical competence. The finding that hypothyroidis m causes decreased bone mechanical competence agrees with another anim al study and a number of human studies, and we conclude that bone qual ity and mechanical competence can be adversely affected by abnormal th yroxine concentrations. (C) 1998 Wiley-Liss, Inc.