Effects of hormones on osteocyte function and perilacunar wall structure.

Microradiographical and ultrastructural aspects of periosteocytic lacunae are determined by osteocytic activity, lacunar modeling and perilacunar miniremodeling in particular. The miniremodeling activity is constituted by two alternating processes: osteolysis and osteoplasis. Modifications of lacunar shape and size and of perilacunar wall ultrastructure, caused by a direct or indirect effect of certain hormones on osteocytic activity, were observed. The lacunar modeling alterations, particularly in cases of VDH or PTH deficiency, result in an irreversible impaired calcification of the lacunar walls and consequently, mottled lacunae. The alterations of periosteocytic osteolysis are characterized by an increase in number of enlarged lacunae and/or by increased magnitude of this lacunar enlargement. Usually observed as an effect of PTH and VDH, these alterations can also be induced by GC, T4, PG. On the other hand, CT causes a decrease in periosteocytic osteolysis. Periosteocytic osteoplasis is characterized by perilacunar bone formation of various aspects and is known to be stimulated by CT. The osteocytic response to hormones is a function of concentration and not of time; it is transient and not integrative. It can be concluded that none of the perilacunar wall modifications observed is characteristic of any particular hormonal effect or metabolic bone disease.