Causes of Fatigue that Slip Through the Cracks

I consider fatigue caused by sinus and nasal issues to be the most common cause of otherwise unexplained chronic fatigue. I’ll describe the evidence for this opinion later but, for now, let’s consider some medical causes that can be missed.

An interesting study examined the amount of iron in the blood of women who were not anemic. Usually an iron deficiency, if severe enough, causes anemia but this study was limited to patients with mild iron deficiency, enough to be noted when examining the blood specifically for iron stores but not enough to cause anemia.

The distinction is an important one. Prior to this study physicians usually thought that iron deficiency would not cause fatigue if the deficiency was not severe enough to cause anemia. The study went on to measure the level of fatigue before and after iron replenishment. The level of fatigue dropped after the iron stores were returned to normal.

Two points are evident from this study: The lack of anemia does not rule out iron deficiency as a cause of fatigue. Additionally, measuring iron stores as simply the level of iron in the blood is inadequate. The iron stores must be measured as “ferritin” a simple and inexpensive blood test but one not always done when evaluating a person for fatigue.

Occasionally low thyroid causes fatigue despite a normal TSH—the usual screening test for low thyroid. TSH comes from the pituitary and increases in the event of a failing thyroid usually providing the earliest clue that the level of thyroid hormone is inadequate.

Occasionally the pituitary is the problem and although the TSH should be climbing as the thyroid fails, it does not. Checking the actual levels of thyroid hormone (T4 and T3) will pick up a thyroid problem even in the event of pituitary insufficiency.

Sometimes an arthritis disease can cause even in the absence of severe arthritis symptoms. Almost always the severity of the arthritic disease seems quite proportionate to the complaint of fatigue. Occasionally this is not so. A person might have rheumatoid arthritis with minor joint problems but have significant fatigue. Treating the rheumatoid arthritis usually causes substantial reduction of fatigue.

A note of caution: The vast majority of individuals with unexplained fatigue and very minor arthritis symptoms do not have positive blood tests for arthritic diseases. Even when the blood tests turn out positive the blood abnormality is, almost always, at a low level, unrelated to the minor arthritis. In these cases treating the person as if the individual did have a serious arthritis disease does not improve the fatigue. In short, arthritis blood tests in the setting of unexplained fatigue are often a “red herring,” but not always.

Occasionally a person may have unexplained fatigue due to a liver problem in the absence of abnormal screening liver function tests. Usually other screening tests, however, denote inflammation.

As mentioned before, the best screening tests to determine if, what appears to be unexplained fatigue, is actually caused by a medical problem are the erythrocyte sedimentation rate (ESR) and the C-reactive protein. Both of these are elevated by any process that causes inflammation. Usually any medical disease that causes fatigue causes inflammation as well.

The ESR and CRP won’t tell you the cause of the problem but do let you know that there is a problem. The absence of ESR or CRP abnormalities does not mean that the cause of fatigue is not physical. However, when these tests are elevated a physical cause of fatigue becomes much more likely.