The thyroid gland in Jamaica

ABSTRACT

This thesis describes some aspects of the anatomy and physiology of the thyroid gland in Jamaicans. The purpose of the investigation was to discover if any alteration occurred in thyroid gland activity as a result of the prevailing tropical conditions. Thyroid glands were collected from consecutive post-mortem examinations at the University Hospital of the West Indies. It was shown that the thyroid gland in the average Jamaican weighted somewhat less than is usual elsewhere, but that this reduction could be accounted for by a general reduction in body weight. It was also demonstrated that in this highly selected population, there was a low incidence of goitre and that there was a very low incidence of thyroid nodules. Thyroid function was estimated using a variety of tests involving the use of radioactive iodine. Following a pilot study using the technique of thyroid clearance of radioactive iodine, thyroid function was estimated in a local population the people all being in good health and living in their normal state. The isotopic studies were combined with estimations of stable iodine excretions. It was shown that the daily excretions of stable iodine were on the lower border of normal. This observation is of special interest when the low incidence of goitre is remembered. These results indicated that there is reduced thyroid function in Jamaicans. It is thought that this represents part of the process of acclimatization to a hot environment. The results have been useful also in establishing normal values for a variety of tests of thyroid function which are used in the University Hospital in Jamaica (AU)