When I was a child (a very long time ago), I would occasionally hear my mother speaking about an overweight neighbour or a friend as having “gland” problems. This diagnosis was delivered in hushed tones as if unsuitable for children’s ears and no one ever used the word obese. The idea that gland problems cause obesity is remarkably persistent, since almost every week in clinic I will see someone who thinks that his or her weight is at least partly, if not entirely, due to this. More often than not, the gland in question is the thyroid and the history is familiar. The patient goes to the GP complaining of lethargy, weight gain etc and a routine blood test shows that they have an under-active thyroid, for which they are then prescribed thyroxine. Both patient and GP take the diagnosis to be a sufficient explanation for the patient’s weight problems and there the matter rests. The GP has done what he/she is trained to do (find an illness and write a prescription) and the patient has a clear explanation as to why they have a weight problem.
In practice, however, an under-active thyroid gland is almost never the cause of obesity. This is precisely why correcting the deficiency with medication usually makes no difference at all to the patient’s weight. The whole matter is further complicated by the fact that obesity itself can produce changes in tests of thyroid function that can make it seem as though the thyroid is under-active, when in fact it is normal. Such tests are often incorrectly interpreted by the family doctor.
It’s perfectly natural for us to look for a physical explanation for our weight problems but I’m afraid that thyroid deficiency – or “gland” problems – is, except in exceptional circumstances, not one of them!
Dr David Ashton
19th January 2011
