Evidence for a Non-Calorigenic Effect of Thyroxin on Erythropoiesis as Judged by Radioiron Utilization.

Effects of Hypophysectomy and Hormone Substitution on Packed-Cell Volume in Chickens

“…For example, Muldowney et al (1957) have observed reduced red-cell mass in hypothyroid humans, and Falkheden et al (1963) noted that red-cell volume was decreased after hypophysectomy in 14 humans. Similar results have been found in thyroidec- Adam and Doljansky (1964), while Meineke and Crafts (1964) found an erythropoietic effect of thyroxin in rats which was independent of the effect on oxygen consumption. Vohnout and Hansard (1967) found a positive relationship between thyroxin degradation rate and total red cell volume in sheep.…”

The Influence of Thyroid Hormones on In Vitro Erythropoiesis

“…Some investigators (6,7,22) have postulated that thyroid hormones exert their erythropoietic action through an elevation of ESF levels. However, others (4,5,23) have described augmented erythropoiesis independent of ESF activity, thus suggesting a direct effect on erythroid precursors. Most recently, Golde et al (8) have provided direct evidence of enhanced in vitro erythropoiesis by thyroid hormones.…”

“…Thyroid hormone increases erythrocyte production in euthyroid experimental animals as well (3). This enhanced erythropoiesis has been attributed to a direct hormonal effect on the erythroid marrow (4,5) and to increased erythropoietin (ESF)l secretion (6,7). However, since the studies were carried out in vivo, the calorigenic effect of thyroid hormones on overall metabolism must also be considered.…”

The Central Nervous System in Regulation of Erythropoiesis

“…Although this remains an important part of the control, re cent studies have changed this view considerably and have in dicated that the hormones have a more specific role in the regula tion of erythropoiesis. Thyroxin (27), testosterone (10), GH (9,17,33) and prolactin (21) have been found to stimulate erythropoiesis and erythropoietin production or interact with erythropoietin in an additive manner (7). The studies by J epson and Lowenstein (21) and in this laboratory* on the effect of ovine prolactin on Fe59 erythrocyte uptake in polycythemic mice may further indicate a direct effect of pituitary hormones on erythropoiesis, at least in * Unpublished data some species.…”

“…The site of action of erythropoietin is still unclear, and the reticulocyte release mechanism almost unknown. The effect of the hormones is no longer considered to be so definitely non-specific since recent work on thyroxin (27), testosterone (10), GH (9,33) and prolactin (9,21) provide evidence that these hormones may act directly in the bone marrow or stimulate erythropoietin production. These studies, as well as the studies of Evans et al (7) on the interaction of erythropoietin and hormones, have renewed the interest in the effect of the hormones on erythropoiesis.…”