Spontaneous myelofibrosis in castrated and ovariectomized NMRI mice

The histopathological appearance of myelofibrosis of the bone marrow is described in aged castrated males, ovariectomized females and in male and female control NMRI mice. The highest incidence of the lesion was observed in ovariectomized and female control mice where more than 90 % of the animals were affected. The presence of myelofibrosis in the bone marrow of ovariectomized females and castrated males indicates that estrogens may not play a major role in the development of the lesion and other hormonal disturbances must also be considered.