A Pituitary Factor Inhibiting the Effects of the Thyroid: Its Possible Role in Aging
Hypothyroidism produces many of the symptoms of premature aging, including greying hair, when it occurs in young persons. The successful “rejuvenation” of young hypothyroid patients with thyroid hormone treatment encouraged early investigators in the 19th century to believe that this endocrine deficiency might contribute to the pathogenesis of aging. Early in this century Benedict and others showed that the 02 consumption rate, as measured by basal metabolic rate (BMR) methods, declined with age. Since a low BMR was supposed to be a relatively specific diagnostic test for hypothyroidism, early investigators were encouraged to treat the aged with thyroid. The treatment was a failure. Medicine was faced with a paradox. Thyroid replacement cured the symptoms of hypothyroidism in young persons. However, when these same symptoms occurred in old, normal persons, replacement was ineffective. With the advent of protein bound iodine measurements as a test for the level of thyroid hormones in the blood, an additional complexity was added. The protein bound iodine levels were found to be constant throughout life (5). Faced with the accumulated evidence, investigators have long ago abandoned any hope of relating hypothyroidism to aging.
KeywordsThyroid Hormone Basal Metabolic Rate Early Investigator Specific Diagnostic Test Grey Hair
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