QUEST Volume 11, Number 3, MAY/JUNE 2004

 

 

Thyroid-Related Myopathy and Statin-Related Myositis

Here are some recent questions and answers taken from MDAs on-line "Ask the Experts" feature. MDA-associated physicians and scientists respond to thousands of these questions every year.

Q: Im a 54-year-old man with hypothyroid myopathy who has improved somewhat using thyroid replacement. I still have weakness and a lot of pain in the muscles
of my legs and arms. I awaken extremely stiff and have difficulty with coordination.

Will thyroid replacement relieve all of the symptoms of hypothyroid myopathy? Is it possible that there are symptoms that will never go away?

REPLY from Lawrence H. Phillips II, MDA Clinic Director, University of Virginia, Charlottesville

A: In general, the symptoms of hypothyroid myopathy resolve more or less completely in response to the establishment of normal thyroid function with medication. The reasons for continuing symptoms in the face of thyroid replacement therapy could include inadequate time or inadequate thyroid hormone replacement therapy.

The healing process takes some time, but its sometimes difficult to be patient.

If you have been hypothyroid and are now on thyroid hormone replacement therapy, your doctor should be monitoring your thyroid function. Some fine-tuning of the dose is often necessary.

In addition, there may be some other cause for your symptoms, such as joint pain and stiffness from arthritis. Or, there may be some other underlying muscle disease.

I suggest that you consult further with your treating physician about these issues if your symptoms persist.

Q: Im a 52-year-old male who was recently diagnosed with drug-induced polymyositis. I was on Lipitor [atorvastatin, for high cholesterol] for almost seven years and had elevated liver enzymes (ALT [alanine transaminase, which can come from either damaged liver or damaged muscle] enzyme two to three times normal) throughout this period.

During those years, I was plagued by fatigue, shortness of breath with no activity, and muscle cramping and soreness. My EMG [electromyogram] indicated marked chronic muscle deterioration in my right arm, but NCV [nerve conduction velocity] studies were normal. My muscle biopsy was normal, although I was off the Lipitor for about eight weeks before it was done, so the test was considered inconclusive.

Does this diagnosis make sense, or are further studies warranted? Its all quite confusing, as my aldolase and other muscle enzymes dont seem to be coming down.

REPLY from Jonathan M. Goldstein, MDA Clinic Director, Yale University, New Haven, Conn.

A: Lipitor is a cholesterol-lowering drug from the statin class. There have been reports of muscle dysfunction in some people taking these drugs and the suggestion that myositis can occur in some cases.

Most people get better when the drug or any drug in the statin class is stopped. However, some dont get better. It would be unusual for the muscle biopsy to be normal, however, even if the drug had been stopped. This sounds confusing, and you should make arrangements to see a neuromuscular expert for an evaluation of you and the biopsy/EMG.

In answer to a similar question from someone with dermatomyositis, Robert E. McMichael, MDA Clinic Director, Neurology Associates of Arlington, Texas, replied:

A: The statin drugs have been associated with development of myositis. Other drugs in this class include Zocor (simvastatin), Lescol (fluvastatin), Pravachol (pravastatin) and Mevacor (lovastatin).

The reports are relatively few, and the information is limited. The term myositis, as used by the Food and Drug Administration in the package insert, is a nonspecific diagnosis [meaning muscle inflammation]. Millions of people take statins. By random chance alone, some of them will develop dermatomyositis.

I havent seen any analysis to indicate that dermatomyositis is more likely to occur in people taking statins than in those not taking statins. Im not certain that theres a clear cause-and-effect relationship between taking any statin and developing dermatomyositis, but theres reason to suspect this is the case.

The relationship between the statin drugs and dermatomyositis or polymyositis needs further study. If drugs such as Lipitor can trigger dermatomyositis, the risk appears to be very small.

When a statin is combined with another class of lipid-lowering drug called fibrates, there appears to be a stronger association with developing an inflammatory myopathy. The statin drugs have also been associated with myasthenia gravis.

The statins can induce an acute type of muscle destruction called rhabdomyolysis, especially when combined with certain drugs, including the fibrates, high-dose niacin, cyclosporine, systemic antifungal drugs and erythromycin.

Rhabdomyolysis is a massive breakdown of muscle and can be very dangerous. The cause-and-effect relationship is clearly established. You may have heard that Baycol [in 2001] has been withdrawn from the market in the United States due to concerns that it seems to be more likely than other statins to induce rhabdomyolysis.

Should statins be used? Current recommendations by experts indicate that we should be using them even more. The statins can significantly reduce the risk of heart attack and stroke. The benefits are tremendous.

Statins save lives and prevent disability. However, despite their good safety record overall, these drugs carry some risk of serious side effects.

Other MDA experts have commented on the use of statins by people who already have neuromuscular diseases.

A: A worsening neuromuscular disease in someone taking a statin medication could be a warning. Unusual muscle pain or cola-colored urine in someone on a statin may indicate acute muscle destruction and should prompt an immediate call to a physician.