Surgery and Healing in the Developing World - Dartmouth-Hitchcock

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314 Surgery and Healing in the Developing World
can be delivered of a neurologically, metabolically normal offspring, even if the treatment
came too late in the mother’s life to reverse the mental retardation experienced
in her own period of in utero development.
An example which can be used to illustrate a nongenetic acquired abnormality
in the adult that might also be present congenitally in a child is hypertrophy of the
heart muscle, the myocardium. In sports medicine, athletes are seen who after a
period of conditioning and training have developed myocardial hypertrophy in order
to compensate for the increased demand of the work load of distance aerobic
effort, such as marathon running. The same abnormality may be found in the newborn
with a ventricular septal defect at birth, whose myocardium hypertrophies to
accomodate the increased flow of shunted blood. In both instances of hypertrophy
of the myocardium, and in the similar phenomenon of thyroid hypertrophy, some
genetic traits may have rendered the individual more susceptible to the stress, but
the abnormality is fundamentally an acquired one, and it can be eliminated from
the somatotype by treatment without the genotype conveying this trait in the absence
of similar stress.
Without a genetically determined trait that would be transmissable through
unimpaired fertility, evolutionary biology lacks the two levers of natural selective
advantage under circumstances of environmental stress.
Nutrient Environmental Stress
One of the environmental stresses that has been common in nearly all parts of
the world at one time or another has been caloric insufficiency. Famines have occurred
from pole to equator under environmental circumstances from drought to
glaciation. There is little suppportable claim that starvation induces hypothyroidism,
but rather that those who have hypothyroidism are better adapted to reduced
calorie intake. Iodine deficient environments have the highest incidence of hypothyroidism—-acquired,
not inherited, in such a micronutrient milieu—and in such
environments hypothyroid individuals could better withstand what would be for
individuals with normal metabolism, macronutrient insufficiency.
As with the endocrine manifestations of diabetes, that even in the adult acquired
form has a genetic predisposition, there may be a genetic predilection for goiter or
for cretinism in some instances. The fetus seems to preferentially sequester more
than the maternal share of iodine-—and this is evidenced by the large goiter growth
during pregnancy of some women under observation in this study who delivered
babies who were marginally compensated, or at least not florid cretins. Cretinism
was prevented by a shifting of the scarce iodine to the fetus at a cost of a more severe
adult acquired goiter; this compensation may be genetically predetermined.
This would reflect an acquired biologic adaptation to energy-resource-poor environments
on the part of those individuals whose energy requirements were minimized
by their depressed metabolic rates acquired by micronutrient iodine deficiency.
Decreased fertility is a collective biologically acquired response that further decreases
demand on caloric resources.
Coincidence, merely by chance association, is an improbable explanation for the
fact that hypothyroidism is found in highest incidence in the world’s calorie
resource-poor regions. Coincidence is also a less satisfactory explanation that these
regions of endemic hypothroidism have not developed as intensely into complex
societies, taking into consideration the effect of this decrease in human energy utilization.