Very little blood is lost except on the physiologic conditions. When there is blood loss such as a nosebleed or a female's monthly loss of blood, the bone marrow senses the blood loss. To understand the disorder, iron is probably the only nutrient which has control mechanism. We don't fully appreciate where that control mechanism is. It is believed to be at the site of absorption.
Studies are now ongoing to determine just where the control mechanism is.
There are no early symptoms of the disorder. It takes decades for enough iron to accumulate in the body. Normally, the amount of iron is rather small. You can appreciate that it may take decades for enough iron to accumulate to damage organs and that amount appears to be between 15 to 25 or more grams of iron. The symptoms depend on the organs damaged.