The influence of growth hormone substitution therapy on erythroid and myeloid progenitor cells and on peripheral blood cells in adult patients with growth hormone deficiency

It has been reported that hypophysectomized rats exhibit normochromic, normocytic anaemia. Pancytopenia with impaired DNA synthesis in the bone marrow can be restored in these hypophysectomized rats by syngeneic pituitary grafts placed under the kidney capsule or treatment with growth hormone (GH). Until now, adults with hypopituitarism have received adequate replacement therapy with thyroxine, cortisol and sex steroids, but not with GH. We therefore investigated the effects of GH replacement therapy on the proliferation and differentiation of erythroid and myeloid progenitor and peripheral blood cells in 11 adult patients with growth hormone deficiency in a double-blind, placebo-controlled study for the first 6 months of therapy. The placebo group showed no changes during the first 6 months without therapy in either insulin-like growth factor I (IGF-I) levels, erythroid and myeloid progenitor precursor cells or peripheral blood cells. After commencement of GH therapy, IGF-I levels rose significantly during 24 months of therapy from 75.3±13.5 to 225±34.7ngmL^?1 (P<0.001). Erythroid and myeloid progenitor precursor cells showed a steep and significant increase after 18 and 24 months of therapy (erythroid: from 10.7±3.5 to 261.4±79.8, P<0.02, after 18 months and to 276.8±149.8 × 10⁵ mononuclear cell colonies, P<0.03, after 24 months; granulocyte–macrophage colony-forming units: from 39.7±9.8 to 316.9±124.6, P<0.002, after 18 months and to 366±188.7×10⁵ mononuclear cell colonies, P<0.03, after 24 months), whereas the peripheral red and white blood cells exhibited only minimal non-significant changes. The principal regulators of erythropoiesis, such as erythropoietin, and parameters reflecting erythropoiesis in the peripheral blood, such as reticulocytes, remained almost unchanged throughout the whole study period. We therefore conclude that patients with GH deficiency do not have anaemia, but have haematopoietic precursor cells in the lower normal range, and that GH substitution therapy over a period of 24 months has a marked effect on erythroid and myeloid progenitor precursor cells but only negligible effects on peripheral blood cells in GH-deficient adults.