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Evolution and your surgeon

Are some thyroid cells ‘vestigial’?

Question from C.D., Canada:

I have recently been seeing a surgeon for some nodules in my thyroid (he thinks it may be a follicular neoplasm and wants to do a thyroidectomy). When I questioned him about how well science understands thyroid function at present and whether medication was enough to replace its function, he said that the thyroid has 2 cell types, one we understand, but the other—calcitonin cells—are just remnants from our reptilian ancestry, and have no use in humans. We don’t like his answer, and feel that he’s too eager to do surgery.

Do you have any information about the thyroid or that might be useful to present to this doctor?

Answer by Dr Carl Wieland

Thanks for your letter. I trained as a medical doctor, and although I cannot give specific medical advice (I have not practised since 1986) I am able to make some comments for information.

The thyroid does contain cells that secrete calcitonin. In fact, it is the major source of calcitonin, although it is manufactured in other parts of the body in small amounts, including the lung.

There is no reason at all to think that the calcitonin-secreting cells in the thyroid are an evolutionary leftover, and I would not agree with that statement at all. For one thing, even if we did not know the function of calcitonin, it would not mean that it does not have a function.

However, we know that it does. Calcitonin has a role of some sort in regulating calcium and phosphorus metabolism (and hence presumably blood levels of calcium), and in fact it has been used as a treatment for osteoporosis—and is available in synthetic form as a nasal spray.

Does this mean that when one removes the thyroid for other reasons, one is losing the calcitonin, and hence should not have the procedure? That does not necessarily follow: for instance, it is also known that the lymphoid cells in the appendix have a function, and in the tonsils, but one can remove them without any disastrous consequences, because the body has a lot of built-in redundancy. E.g. one can lose a gallbladder, and not have major problems, even though the gallbladder has a very definite function.

As far as I am aware, when one removes the thyroid, the level of calcitonin does drop, despite other parts of the body still making some calcitonin. It does not appear to have any adverse effects on the serum calcium levels, however. This may be because other mechanisms, such as parathyroid hormone made in other glands, can compensate. Is there any evidence that there is an increased risk of say osteoporosis (‘thinning’ or ‘brittling’ of the bones) from losing the thyroid? I do not know. It may pay to do a lengthy internet search for this, and in any case I would suggest that you seek a second specialist opinion. Because even if there was an increased risk, say, it may be that the risk of not removing it is even greater than that. For what it is worth, my own mother had a total thyroid destruction many years ago, and is functioning very well at 83 years of age.

Summary:

1. It is totally mythical to suggest that any cells in the thyroid are useless evolutionary leftovers

2. It does not therefore follow that you should necessarily reject the advice for the gland’s removal. That would depend on the overall balance of factors.

3. I would strongly suggest that you seek urgent additional specialist medical advice, and combine it with (weigh it against) the advice you have already received, ignoring the evolution-inspired nonsense, but being careful not to throw out the baby with the bathwater.

Hope that helps,

Carl Wieland