Doctors Lounge - Hematology Answers
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Forum Name: Hematology Topics
Question: Symptoms of anemia but CBC is normal?
|gingersnaps34 - Thu Jun 10, 2010 5:42 am||
I was diagnosed with iron deficiency anemia in 2007 as a result of my gastric bypass surgery. Nothing would work except getting iron through an IV. They first caught it because they stated my ferritin lvl was at 2. The IV's worked and I felt fine. After this I moved out of state. I started feeling really bad again headaches, muscle pain and weakness, shortness of breath, dizzy spells and I fell 2 times in one week. I finally went into the ER and they did a CBC but it came out normal! Can a CBC be normal if my Ferritin lvls are low or should I get checked out for something else besides Anemia?
|Dr.M.Aroon kamath - Sat Jul 31, 2010 6:07 am||
Iron deficiency often develops very insidiously. Stored iron in the bone marrow is the first to become depleted. Serum ferritin levels start to decrease following this, while the Hct, Hgb and MCV remain normal. A drop in the iron ferritin level occurs before any depletion in serum iron (as seen in iron-deficient anemia) and may decrease significantly without any obvious symptoms whatsoever.
At least some of the reasons for the difficulties in the interpretation of serum ferritin levels are due to a number of laboratory-related factors such as,
- the presently available ferritin immunoassay kits, which lack accuracy and reproducibility especially in the lower end of the reference range of 20-150 ug/L. The lower edge is rather too close to ‘0’.
- the problems faced by the laboratories in establishing genuine reference ranges in the face of sub-clinical iron deficiency in the apparently ‘normal’ general population without evidence from bone marrow aspiration.
- setting a “cut off” point for diagnosing iron deficiency due to many invalidated reference ranges in common use (many use a cutoff level of 12ug/L, while the literature frequently quotes a figure of 10-20ug/L).
Ferritin concentration indicates how much iron is stored in the body. As ferritin is one of the “acute-phase proteins”, measured levels may be normal or elevated in infective, inflammatory (especially rheumatoid arthritis), chronic granulomatous diseases or malignant disease in the setting of iron deficiency. Serum ferritin level is also increased by excessive alcohol intake. In the absence of one of these conditions, if ferritin is low, one may attribute the low serum ferritin levels to iron deficiency and begin treatment. A careful clinical history, ESR and serum C-reactive protein level can be of help to identify such conditions. However, It is also extremely rare for ferritin levels to be to be falsely low.
One study compared serum ferritin concentrations with iron stores in the bone marrow for unexplained fatigue in non-anaemic women and found that
- some women with very low iron stores in the marrow still have ferritins between 16 -20 ug/L and
- that a serum ferritin concentration of 50 µg/l was associated with a 50% chance of iron deficiency occurring in the bone marrow. Significant response to oral iron supplements was observed only in the patients with a baseline serum ferritin concentration <50 µg/l.
(Verdon F, Burnand B and Stubi CL et al. Iron supplementation for unexplained fatigue in non-anemic women: double blind randomized placebo controlled trial. BMJ. 2003 May 24;326(7399):1124).
Iron-thyroid connection: insufficient iron levels theoretically can affect the first two of three steps of thyroid hormone synthesis in the thyroid gland by reducing the activity of the enzyme thyroid peroxidase, which is iron dependent. Conversely, iron deficiency may also affect metabolism by reducing the conversion of the ‘inactive’ T4 to the ‘active’ T3 form in the tissues. Low iron levels also are believed to increase the levels of Thyroid Stimulating Hormone (TSH).
Some studies have raised doubts about this connection. One such study concludes thus,
“There was no association between thyroid function and serum ferritin levels. We conclude that serum ferritin levels do not account for the relation between subclinical hyperthyroidism and vascular mortality”.
In your case (as i already mentioned), it is extremely rare for ferritin levels to be to be falsely low. Therefore, it is likely that the iron therapy was just not optimal to correct the deficit in your bone marrow. Also, in resistant cases, any associated underlying disorder (mentioned earlier) that may be contributing to the iron deficiency should be sought. Any ongoing blood loss also has to be looked for. Some of these disorders impair erythropoiesis by decreasing both erythropoietin (EPO) production and marrow responsiveness to EPO. A bone marrow examination will help to confirm the diagnosis.
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