Marked erythropoietin increase before fall in Hb after treatment with cytostatic drugs suggests mechanism other than anaemia for stimulation.

Serum erythropoietin (Epo) was measured in 23 patients before, during and after intensive cytostatic treatment courses for acute leukaemia or before bone marrow transplantation. A marked increase was seen in all patients, starting 1 or 2 d after initiation of treatment. A peak was reached after about 7 d, at levels as high as 1450 IU/l, after which Epo fell rapidly, even in patients who were anaemic at that time. In 13 of the patients there was no fall in Hb level that could explain the increase in Epo. The increase was too large to be explained by an altered Epo metabolism or marrow utilization. Cytostatic drugs cause an increase in Epo production not mediated through anaemia, possibly initiated by a cytostatic effect on the kidneys or by an unknown stimulatory factor, responsive to bone marrow inhibition.