The role of iron in mediating testosterone's effects on erythropoiesis in mice

Haematological actions of androgens

In this review, we discuss the effects on androgens on the haemopoietic system, focussing largely on the effects of testosterone on erythropoiesis. Stimulation of erythropoiesis is one of the most consistent effects of testosterone treatment observed in clinical trials. In men with anaemia this effect can be beneficial. Conversely, erythrocytosis is one of the most common adverse effects of testosterone treatment with a relative risk of 8.14 (95% CI: 1.87-35.40) estimated by a recent meta-analysis of randomised placebo controlled clinical trials. A reduction in haemoglobin is commonly seen in men receiving androgen deprivation therapy for prostate cancer, and in transwomen receiving gender affirming therapy to reduce serum testosterone. While mechanisms by which androgens regulate erythropoiesis are not fully understood, it is likely that effects on erythropoietic progenitor cells and erythropoietin are involved, with secondary effects on iron metabolism. In contrast, whether androgens exert clinically relevant effects on white blood cells and on platelets requires further study.

Iron Mining for Erythropoiesis

Iron is necessary for essential processes in every cell of the body, but the erythropoietic compartment is a privileged iron consumer. In fact, as a necessary component of hemoglobin and myoglobin, iron assures oxygen distribution; therefore, a considerable amount of iron is required daily for hemoglobin synthesis and erythroid cell proliferation. Therefore, a tight link exists between iron metabolism and erythropoiesis. The liver-derived hormone hepcidin, which controls iron homeostasis via its interaction with the iron exporter ferroportin, coordinates erythropoietic activity and iron homeostasis. When erythropoiesis is enhanced, iron availability to the erythron is mainly ensured by inhibiting hepcidin expression, thereby increasing ferroportin-mediated iron export from both duodenal absorptive cells and reticuloendothelial cells that process old and/or damaged red blood cells. Erythroferrone, a factor produced and secreted by erythroid precursors in response to erythropoietin, has been identified and characterized as a suppressor of hepcidin synthesis to allow iron mobilization and facilitate erythropoiesis.

Wuzi-Yanzong prescription alleviates spermatogenesis disorder induced by heat stress dependent on Akt, NF-κB signaling pathway

Akt and nuclear factor kappa B (NF-κB) signaling pathways are involved in germ cell apoptosis and inflammation after testicular heat stress (THS). We observed that after THS induced by the exposure of rat testes to 43 °C for 20 min, their weight decreased, the fraction of apoptotic testicular germ cells significantly increased, and the proliferation of germ cells was inhibited. In addition, THS lowered serum testosterone (T) level, whereas the levels of follicle stimulating hormone and luteinizing hormone were not significantly changed. The ultrastructure of the seminiferous tubules became abnormal after THS, the structure of the blood-testis barrier (BTB) became loose, and the Sertoli cells showed a trend of differentiation. The level of phosphorylated Akt was reduced, whereas the amount of phosphorylated NF-κB p65 was augmented by THS. Wuzi-Yanzong (WZYZ), a classic Chinese medicine prescription for the treatment of male reproductive dysfunctions, alleviated the changes induced by THS. In order to determine the mechanism of action of WZYZ, we investigated how this preparation modulated the levels of T, androgen receptor (AR), erythropoietin (EPO), EPO receptor, and Tyro-3, Axl, and Mer (TAM) family of tyrosine kinase receptors. We found that WZYZ activated the Akt pathway, inhibited the Toll-like receptor/MyD88/NF-κB pathway, and repaired the structure of BTB by regulating the levels of T, AR, TAM receptors, and EPO. In conclusion, these results suggest that WZYZ activates the Akt pathway and inhibits the NF-κB pathway by acting on the upstream regulators, thereby improving spermatogenesis deficit induced by THS.

Markers of Iron Flux during Testosterone-Mediated Erythropoiesis in Older Men with Unexplained or Iron-Deficiency Anemia

CONTEXT

Testosterone treatment of hypogonadal men improves their hemoglobin, but the mechanism is not understood.

OBJECTIVE

To investigate possible mechanisms by which testosterone stimulates erythropoiesis in hypogonadal older men with unexplained or iron-deficiency anemia.

DESIGN

The Anemia Trial of The Testosterone Trials, a placebo-controlled study in older, hypogonadal men.

SETTING

Twelve academic medical centers.

PARTICIPANTS

A total of 95 hypogonadal men (testosterone < 275 ng/mL) ≥65 years with anemia (hemoglobin < 12.7 g/dL). They were classified as having unexplained (n = 58) or iron deficiency anemia (n = 37).

INTERVENTION

Testosterone or placebo gel for 1 year.

MAIN OUTCOME MEASURES

Markers of iron metabolism during the first 3 months of treatment.

RESULTS

Testosterone replacement significantly (P < 0.001) increased hemoglobin in the 58 men who had unexplained anemia (adjusted mean difference 0.58 g/dL; 95% confidence interval, 0.31-0.85). Testosterone replacement tended to increase hemoglobin in the 37 men who had iron deficiency (0.38 g/dL; -0.19, 0.95), but the response was more variable and not statistically significant (P = 0.19). In men with unexplained anemia, testosterone replacement suppressed hepcidin (-8.2 ng/mL; -13.7, -2.7; P = 0.004) and ferritin (-19.6 µg/L; -32.8, -6.3; P = 0.004), but in men with iron deficiency, testosterone replacement did not. The decrease in hepcidin was moderately correlated with the increase in hemoglobin in the men with unexplained anemia (correlation coefficient -0.35, P = 0.01) but not in those with iron deficiency anemia (correlation coefficient -0.07, P = 0.73).

CONCLUSIONS

Testosterone replacement of older hypogonadal men with unexplained anemia stimulates erythropoiesis associated with increased iron mobilization. This effect appears to be attenuated by iron deficiency.