What is iron deficiency?

- [Voiceover] Iron deficiency anemia is anemia due to a deficiency in iron, and this is a type of microcytic anemia, but that's something you already know, because of this diagram in which you saw that iron is a really important component of heme, and heme is essentially half of hemoglobin, right? So that if you don't have iron, you certainly can't make heme and without heme, you can't make hemoglobin. Any time you have a problem with making hemoglobin, you end up with a microcytic anemia. A microcytic anemia refers to an anemia where you end up with really small red blood cells. So why does that happen? Is that just something that happened by accident? Well, no, it's something that the body does intentionally. So, in any condition where you have a problem with making hemoglobin, such as with iron deficiency anemia, you end up with these red blood cells that have fewer hemoglobin molecules than they should. So you see something like this, where you have this big old cell with very little filling on the inside. The body responds to this by cutting this red blood cell in half so that you end up with smaller red blood cells like this and each has a small amount of hemoglobin on the inside, but the point is that the concentration of hemoglobin inside each of these really small cells is essentially very close to what you'd see in a normal cell. It's almost like if you had a jelly donut that had very little jelly on the inside and so the donut shop tried to make up for that by shrinking the donuts down into munchkins so that you have these really little munchkins that were filled plump with jelly on the inside. Okay? If you already know all that about iron deficiency anemia, what is there left to learn? Well, one of the things we haven't talked about is the causes of iron deficiency anemia so we'll talk a little bit about the causes of iron deficiency anemia. I like to think of the different causes as belonging to one of four different groups. As you can probably tell, I like to think of things in terms of groups because it helps organize my thinking. I do very little memorization and more rationalization. Alright? So when you usually think of iron deficiency, you're probably most likely to think of a person who isn't taking in enough iron through their diet. You're probably most likely to think of cause of decreased intake, decreased dietary intake. We get iron through the diet in foods like green leafy vegetables and meat, so certainly somebody who isn't taking enough quantities of these types of foods will have iron deficiency but really, decreased intake is most problematic in little infants. Little infants. Especially those infants less than six months old and that's because when you're younger than six months old your diet consists almost entirely of breast milk and breast milk is a really poor source of iron. That's why infants end up with iron deficiency and then iron deficiency anemia, alright? So, another cause of iron deficiency is an increase in the body's demand. Increase in the body's demand of iron. Really, you'll see this in one of two types of patients. The first type of patient is either a child or an adolescent. Adolescent... The second type of patient you'll see this in is a pregnant woman. Pregnant... a pregnant woman. Okay? So you know that during childhood and adolescence we undergo a really rapid rate of growth and along with that rapid rate of growth, we experience a rapid expansion in our blood volume, so our blood volume has to increase as well. In order to increase the blood volume, the number of red blood cells has to increase. You can't increase the number of red blood cells if you don't increase hemoglobin production. That increase in hemoglobin production requires increased iron. That's what accounts for the increase in the body's demand of iron during childhood and adolescence. You see something very similar going on in pregnant women. During pregnancy, you can see up to a 20 percent increase in your blood volume to accommodate the needs of the growing fetus inside the woman. That accounts for the increase in the demand, the body's demand of iron. It's very easy for these two types of patients to not take in enough iron through the diet to meet the increase in the body's demands and that's how they end up with iron deficiency. So let's say you have a patient, then, who's taking in enough iron through the diet but for some reason or another, that iron isn't making its way through the gut and into the body. What I mean to say is let's say there's a problem or a decrease in the absorption. In the absorption of iron. To understand the different situations that could lead to a decrease in the absorption of iron, we'd have to talk about how the absorption of iron normally occurs. So, here's a man, okay? The reason why I put him in here is to show you that when you take in iron through the diet, it goes in through the mouth, through the esophagus, through the stomach and then to this point. This point right here called the duodenum. The duodenum. Okay? So the duodenum is a point where you really absorb almost all of your nutrients, including iron. Before iron makes its way through the duodenum and it's absorbed in the duodenum, it has to go through the stomach, and it's really important for the iron to pass through and encounter the stomach because the stomach contains lots of acid. That's what I'm drawing in green over here. Contains lots of stomach... contains lots of stomach acid. The stomach acid is essential for converting the iron that you take in through your diet into a form that is more easily absorbed through the duodenum. It's really important for serving that function. So, going back to this diagram that we're making over here, there are really two ways that you could end up with a problem in the absorption of iron. The first way is you could just not be making enough stomach acid, so you have a decrease in the production of stomach acid. The second cause, the second way you could end up with a problem in the absorption of iron is having some sort of problem, some sort of problem in the duodenum. In the duodenum... In the duodenum. So, first let's talk about this decreased acid production. This really happens very commonly in two types of patients. The first is the patient who is taking a drug called a proton pump inhibitor. I've abbreviated that PPI, so proton pump inhibitor. So that's a type of medicine you take for the treatment of esophageal reflux disease, acid reflux disease, so that's a disease in which you have acid refluxing, or going backwards from the stomach into the esophagus and it causes irritation of the esophagus, most commonly referred to as heart burn. In order to relieve the symptom of the heartburn, patients will take a drug called a proton pump inhibitor that decreases the production of this stomach acid. Now, with decreasing the production of stomach acid, you get relief in the symptom, but along with that, you get a reduction in the absorption of iron through the duodenum. Okay, so that's one way in which you could end up with a problem in the absorption of iron. A second type of patient in which you'll see a decrease in the production of stomach acid is a patient who has had a gastrectomy. A gastrectomy. A gastrectomy refers to either the partial or the entire removal of the stomach. Why would somebody have either part of their stomach or their entire stomach removed? Well, there could be a couple of different reasons why this would occur, but first is it could be done for weight loss reasons. To aid in weight loss. The second reason is it could be done to remove a stomach cancer, or even, perhaps, a stomach ulcer. For whatever reason, the point that we're focusing on over here is with the removal of part of the stomach, you have a decrease in the production of stomach acid which decreases the conversion of iron into the form that's more easily absorbed by the duodenum leading to iron deficiency, and then leading to iron deficiency anemia. Alright? So that's the first cause of an impaired absorption of iron. The second cause occurs with some dysfunction in the duodenum, or some problem in the duodenum and really, you see this in patients who have celiac, celiac disease. Celiac disease refers to patients who have an intolerance of gluten. Gluten is something that's found in different foods in your diet. It's found in wheat, barley, rye, and other types of similar food. When patients with celiac disease encounter these, encounter gluten in their diet, it leads to an inflammation and a destruction of the cells in the duodenum so that the duodenum doesn't do as good of a job absorbing nutrients, including iron. So that's how patients with celiac disease end up with iron malabsorption, or a decreased absorption. So, finally, we have to consider what I think is the most important cause of iron deficiency anemia. So let's say you have a patient who's taking in enough iron through their diet and all of that iron is making its way into the body, but for some reason or another, they have an increase in the loss of iron from the body, usually you see this with blood loss, okay? Because with blood loss, you lose the red blood cells and then with that comes a loss of the hemoglobin inside the red blood cells, and with that comes a loss of the iron that's inside the hemoglobin, right? So that's how you end up with iron deficiency. You see this in a few different cases. The first especially encountered, or really only encountered in young women who have not yet encountered menopause, is heavy menstrual bleeding. Heavy menstruation. Another cause is peptic ulcer disease, which I've abbreviated PUD. Peptic ulcer disease refers to when you have ulcers either in the duodenum or sometimes in the stomach, and a lot of times these ulcers can bleed and with that increase in blood loss, you can end up with iron deficiency, right? One of the most important causes of increased blood loss leading to iron deficiency is colon cancer, okay? Most often encountered in elderly patients and colon polyps. The reason why this is so important, aside from the increase of mortality that you see with this condition, is because a lot of times this goes unnoticed to the patient so the patient doesn't notice that there is blood being lost through the GI tract in their stool. It's usually only when an elderly patient presents with iron deficiency anemia and you work up that iron deficiency anemia and try to figure out what the cause of it is that you discover that he or she has an underlying colon cancer. It's something to always keep in the back of your mind, especially when an older person presents with colon cancer. Alright, so then let's finally discuss one of the most common causes of blood loss in developing countries, and that is a hookworm infection. These hookworms can inhabit your intestine and literally latch themselves on to the wall of your intestine and suck out blood, leading to blood loss. These are the different causes, lots of the most commonly encountered causes of iron deficiency anemia. Keep in mind that iron deficiency leads to a problem with making hemoglobin which then, ultimately leads to a microcytic anemia.