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Steroids are one of the cornerstones in the treatment of autoimmune disease, such as myasthenia gravis (MG). Many patients are very reluctant to embark on treatment with steroids, such as prednisone or prednisolone. This is mostly because of fear of side effects associated with these drugs. Whilst this is justified to a certain extent, they are actually closely related to a human hormone, called cortisone.

The molecular structure of Cortisone, Prednisone and Prednisolone are very similar.

Human steroids, such as cortisone, are produced by our adrenal glands. They are essential for human life.

Steroids have complex biological effects on numerous tissues in our bodies. We use the effect on the immune system in the treatment of MG. The effect on bone, skin, other hormones, eyes etc. explain the side effects seen with steroid therapy.

These side effects resemble closely a disease caused by overproduction of steroids (for example by a tumour of the adrenal glands) called Cushing’s disease. As such, the problem in steroid use in medicine is not whether or not one takes steroid medicaton, it is solely the dose of steroids that is important.

The human body produces about 30mg of cortisone per day. The biological effect of this can be simulated with about 8mg of prednisone or prednisolone. Because of this, most side effects associated with prednisone only become evident at doses higher than 8mg/day. With lower doses, the adrenal gland simply produces less cortisone, trying to balance things out. With doses higher than 8mg/day, symptoms of Cushing’s syndrome will appear, because – even if the adrenal gland is completely switched off, and produces no cortisone at all – the hormonal effects of the prednisone are more than what are bodies are used to.

Often patients with severe MG are forced to initially take high doses of prednisone for a few weeks or months. Side effects are very common with this, but are often tolerated as this is one of the quickest ways to get MG under control. In the longer run, the aim is often to decrease steroid doses to a minimal dose. This is mostly only possible by combining steroids with a steroid-sparing medication (Azathioprine, Mycophenolate, Methotrexate, etc.). These have a very slow onset of action – up to 2 years! – but are very helpful in minimizing steroid doses long-term.

Interestingly enough, prednisone in doses lower than 8mg/day still appears to have an effect on the immune system. It is often difficult to completely stop prednisone, as previously well controlled MG can re-occur. It is important to know that with doses clearly lower than 5mg/day, long-term side effects of prednisone are minimal.

In summary, a lot of the bad name that steroids have is not quite justified: These drugs can have severe side effects if overused for long periods of time. On the other hand, careful use, especially in lower doses, remains one of the cornerstones of MG treatment and can be done very safely.

LEARNING BITE (by Dr Fiona Chan)

If you are used to taking large doses of steroids for some months, the adrenal gland has nothing to produce for a long while, and ceases to function properly. This is important to realize in 2 scenarios: If steroids are then stopped suddenly, the adrenal glands can’t kick in to produce the cortisone needed for survival, and patients can become very unwell because of the lack of steroids.

During an infection or other physically stressful event, steroid production by the adrenal gland would usually go up in such a scenario (Steroids are hormones our body releases during stress), but because the adrenal gland is not functional, there is too little steroids in the circulation, your body is then unable to react adequately during the stressful event and the disease process can worsen.

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