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Abstract

Endemic goitre due mainly to iodine deficiency
has been recorded in many areas of the world throughout
history and its response to crude iodine preparations
has been noted. The good effect of the
pure element in the treatment of goitre was modified
by severe thyrotoxic reactions, reported particularly
from areas of endemic goitre.
A rational basis for the use of iodine in prophylaxis
against goitre, came with the discoveries
linking iodine with thyroid metabolism and measurements
of low iodine concentrations in water, soil
and plants. Mountainous areas which are far from the
sea and have been subjected to glaciation in the last
Ice Age are particularly prone to iodine deficiency.
The excellent response to iodine prophylaxis in preventing
goitre in the children of Ohio, U.S.A. was
followed by an equally good one in Switzerland.
However there were further reports of thyrotoxicosis
following iodine prophylaxis again occurring
in adult goitrous females. It was thought by those
who believed that iodine caused thyrotoxicosis in some
people, that the size of' thedose given was important
but examples suggest that this was not so. Indeed
many authorities denied the existence of iodbasedow.
Tasmania has been a very satisfactory area to
observe these phenomena. Population shifts are
minimal and it was a moderately iodine deficient island
with a goitre incidence among adult females of approximately
30 per cent. Although goitregens were pro- posed as a contributing cause of goitre none such have
been found. Iodation of bread gave universal prophylaxis
to the population and an excellent response
has been achieved. Goitre prevalence in children has
fallen to that seen in countries where goitre is not
endemic.
The pathology of goitre in Tasmania is similar
to that seen in all parts of the world. There does
not seem to be any increased incidence of thyroid
cancer, cretinism is rare and before iodation of
bread the incidence of thyrotoxicosis was lower than
that recorded in iodine sufficient communities. Several
factors have combined to produce a change in
iodine content in the environment of Tasmania, before
iodation of bread. The importation of large amounts
of food from areas of Australia which are not iodine
deficient and the use of iodophors in the food industry
provided extra iodine. Several other sources of iodine
were brought to Tasmania resulting in a gradual increase
in iodine consumption.
A steady increase in the incidence of thyrotoxicosis
was noticed from 1960, as shown in Fig. 10-2
with a sudden rise which has continued from 1966 when
bread was iodated. It is suggested that the incidence
of thyrotoxicosis has risen to that occurring in nonendemic
goitre areas, previous iodine deficiency having
protected those otherwise prone to develope the disease.
If this is so, the incidence will remain similar to
that of the average world incidence for non-endemic goitre areas, but the age group affected should become
progressively younger. The addition of iodine to the diet of the population
of Tasmania can be justified by the disappearance
of goitre and consequent decrease in
thyrocardiac disease which is associated with nodular
goitre in middle age, the probable disappearance of .
lethal cancer of the thyroid in the elderly, tracheal
obstruction by retrosternal goitre and the cosmetic
effect in females who formed the majority affected by
the condition.
It is predicted that the price for this will be
a slight increase in the incidence of thyrotoxicosis
in an age group which will become progressively
younger and more able to cope with the disease. On
balance at the present time this price is reasonable.
Evidence to support these assumptions are presented
in the body of the thesis.

Item Type:	Thesis - PhD
Authors/Creators:	Connolly, Roger
Keywords:	Hyperthyroidism
Copyright Holders:	The Author
Copyright Information:	Copyright 1972 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).
Additional Information:	Bibliography: p.188-232. Thesis (M.D.) - University of Tasmania, 1972
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