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Normal Thyroid Size



What can be considered as a normal thyroid size will, in fact, depend on many different criteria.
Your age, gender, home country and whether or not you are a smoker all have a significant part in deciding if your thyroid size could be described as ‘normal’.

In most modern, developed countries, the dimensions of a normal sized thyroid range from 4 to 4.8 x 1.0 to 1.8 x 0.8 to 1.6 cms but being outside of this range does not automatically imply problems.

The general preconception nowadays is that the thyroid, for most people, is not easily discernible on the surface of the skin and cannot generally be felt upon palpitation by a doctor’s hand on examination. It is, therefore, fairly invisible to most of us.


Certainly it is fairly apparent that in countries such as Japan, Iceland, the USA and Britain, where there is generally a good daily intake of iodine, most people will have a thyroid on the smaller side of those previously mentioned dimensions. Countries where there is more likely to be an iodine sufficiency tend to have people with larger thyroids. In the areas where there is considered to be sufficient iodine, the thyroid often becomes smaller in the second half of the life cycle; in other places, it will remain more or less the same size.

Men will generally have larger thyroids than women. This could well be a reflection of a correlation between body mass and thyroid size. It is also generally recognised that a woman’s thyroid volume will increase during her pregnancy.

There is additionally a clearly established link, after many scientific studies, between smoking and thyroid size. The more you smoke, the larger your thyroid. Some studies are currently investigating whether this association is even greater in areas of iodine deficiency, as is suspected.

It is, furthermore, acknowledged that there is a link between genetic make-up and thyroid size. A person’s individual genetics will have a distinct influence on the growth of thyroid gland cells.

The size of the thyroid can be precisely and reliably gauged by use of ultrasonography, which is safe, easy to use and now quite portable. More and more doctors are now able to use ultrasonography in their surgeries to establish thyroid size, which is a far more accurate method than the previous palpitation technique.

As can be seen, therefore, it is distinctly possible for two people to have thyroids of quite different sizes but for them both to be diagnosed as ‘normal’ by a doctor.