The level of the haemoglobin is higher in men than women. why it so?

First a little brush up on physiology:

Hemoglobin is present in our red blood cells (RBCs). The body maintains the RBC count by erthropoiesis( secreted from kidney)which stimulates the bone marrow which produces later forms RBCs. Anemia is a condition that develops when there is less amount of hemoglobin in the body.

Now the reasons for men having higher hemoglobin are:

1. Testosterone- this hormone directly stimulates erthropoietin hormone. As a result, more RBCs produced = more hemoglobin and less anaemia.
2. Menstruation- though this is not a major factor in women normally, but can affect those having either heavy blood loss during the period or having increased frequency of cycles so there is more frequent blood loss.
3. Socioeconomic and cultural conditions- Women in many Indian families are malnourished right since birth or neglected recieving less nutritious food than their male counterparts. Even after marriage, in some families women eat after everyone has finished. Having less nutritious food or food devoid of iron can severly affect the RBC production in body as these nutrients are required for production of RBCs and indirectly Hemoglobin.
4. Pregnancy- an average vaginal delivery involves loss of 500 ml of blood. To restore hemoglobin levels and for maintaining them, a minimum of two years are required before having the next child. If she has children without adequate spacing, chances of having anaemia are increased. The problem is worsened when she has multiple births, taking care of a large number of children and from a poor socioeconomic family.