Gw. Geelhoed, Metabolic maladaptation. individual and social consequences of medical intervention in correcting endemic hypothyroidism, NUTRITION, 15(11-12), 1999, pp. 908-932
Endemic hypothyroidism has been studied in a Central African population in
remote Congo (ex-Zaire)to investigate the prevalence, severity, causes, and
potential control of this disorder, with questions as to why this disease
is conserved, and whether it confers any adaptive advantage in this resourc
e-constrained environment. Iodine deficiency, cassava goiterogens, and sele
nium deficiency were found to be the factors implicated in the severe hypot
hyroidism expressed in congenital cretinism and high goiter incidence in th
is isolated population, which continues to be under observation following m
edical intervention. Profound hypothyroidism was encountered in whole villa
ge populations as measured by serum thyrotropin determinations ranging from
very high to over 1000 IU, and thyroxin levels ranging from low to undetec
table; cretinism rates were as high as 11% and goiter incidence approached
100%. Assessment of endocrinologic status,caloric requirement, energy outpu
t, fertility, and ecologic factors was carried out before and during iodine
repletion by depot injection. Hypothyroidism was corrected and cretinism e
liminated in the treatment group, with goiters reduced in most instances (w
ith regrowth exhibited in some who escaped control) and some symptomatic go
iter patients were offered surgical treatment for respiratory obstruction.
Individual patient benefits, including improved strength and increased ener
gy output, were remarkable. The social and developmental consequences obser
ved within the collective groups of treated patients were remarkable for an
increase in caloric requirement and a dramatic increase in fertility that
led to quantitative as well as qualitative increases in resource consumptio
n. Micronutrient iodine repletion was not accompanied by any concomitant in
crease in macronutrient supply, and hunger and environmental degradation re
sulted. The highly prevalent disease of hypothyroidism is found in highest
incidence in areas of greatest resource constraint. It may be that hypothyr
oidism is conserved in such areas because it may confer adaptive advantage
in such marginal environments as an effect, as well as a cause, of underdev
elopment Hypothyroidism may limit energy requirements, fertility, and consu
mer population pressure in closed ecosystems that could otherwise be outstr
ipped. Single factor intervention in a vertical health care program not sen
sitive to the fragile biologic balance and not part of a culture-sensitive
development program might result in medical maladaptation. (C) Elsevier Sci
ence Inc. 1999.