Mosekilde, L. & Melsen, F. Morphometric and dynamic studies of bone changes in hypothyroidim. Aota path. microbhl. scand. Sect. A, 86: 56-62, 1978. Born biopsies were performed after tetracycline double-labelling by transfixing the right iliac crest in fourteen hypothymid patients. The bone changes in cortical and trabecular bone were determined by s:mple measurement and point counting on decalcified and undecalcified stained sections and compared to normal controls and to sex and age matched hyperthyroid patients. The amount of trabecular bone and the cortical porosity were unchanged in the hypothyroid patients compared to normal controls, whereas the mean oortical thickness was increased. The amount of osteoid and the length of the oaeoid seams were normal, whereas the mean width of the osteoid seams was decreased. The linear calcification rate in cancellous bone was decreased, as were the active calcification surfaces (tetracycline-labelled) and the percentage of osteoid covered surfaces active in mineralization. The mteoclastic resorption surfaces were unchanged in trabecular bone, whereas the osteoclastl activitty in cortical bone was decreased. The osteocytic outeolysis was normal. The bone changes in hypothyroidism were opposite to the changes in hyperthvroidism charaoterized by a very low bone turn-over w:th a reduced osteoid apposition and bone minerahization rate, an inaotive osteoclastic resorption in trabecular bone and a decreased mteoclastic resorption in captical bone. Mewre hiiumlolagique de la mitsse et de la r6mrption dw travees wseuses. Path. Biol. 12: 23, 24, Castro, J . H., Genuth, S. M., Klein, L.: Comparative response to parathyroid hormone in 1238-1243, 1964.