US Thyroid Epidemic
Whilst being interviewed by Radio New Zealand's Kim Hill, Theo
Colborn was quizzed about the endocrine disrupting effects of soy,
Colburn made reference to the thyroid "epidemic" that had afflicted
infants fed soy formulas in the late 1950's and early 1960's.
The Colorado Thyroid Disease Prevalence Study provides disturbing
evidence that the general population in the US is on the brink of an
epidemic of thyroid disease and Soy Online Service believes that the
increased use of soy products is to blame:
The Colorado Thyroid Disease Prevalence Study
Arch Intern Med. 2000;160:526-534
Gay J. Canaris, MD, MSPH; Neil R. Manowitz, PhD; Gilbert Mayor, MD;
E. Chester Ridgway, MD
Context The prevalence of abnormal thyroid function
in the United States and the significance of thyroid dysfunction remain
controversial. Systemic effects of abnormal thyroid function have not
been fully delineated, particularly in cases of mild thyroid failure.
Also, the relationship between traditional hypothyroid symptoms and
biochemical thyroid function is unclear.
Objective To determine the prevalence of abnormal
thyroid function and the relationship between (1) abnormal thyroid
function and lipid levels and (2) abnormal thyroid function and
symptoms using modern and sensitive thyroid tests.
Design Cross-sectional study.
Participants Participants in a statewide health
fair in Colorado, 1995 (N = 25,862).
Main Outcome Measures Serum thyrotropin
(thyroid-stimulating hormone [TSH]) and total thyroxine (T4)
concentrations, serum lipid levels, and responses to a hypothyroid
symptoms questionnaire.
Results The prevalence of elevated TSH levels
(normal range, 0.3-5.1 mIU/L) in this population was 9.5%, and the
prevalence of decreased TSH levels was 2.2%. Forty percent of patients
taking thyroid medications had abnormal TSH levels. Lipid levels
increased in a graded fashion as thyroid function declined. Also, the
mean total cholesterol and low-density lipoprotein cholesterol levels
of subjects with TSH values between 5.1 and 10 mIU/L were significantly
greater than the corresponding mean lipid levels in euthyroid subjects.
Symptoms were reported more often in hypothyroid vs euthyroid
individuals, but individual symptom sensitivities were low.
Conclusions The prevalence of abnormal biochemical
thyroid function reported here is substantial and confirms previous
reports in smaller populations. Among patients taking thyroid
medication, only 60% were within the normal range of TSH. Modest
elevations of TSH corresponded to changes in lipid levels that may
affect cardiovascular health. Individual symptoms were not very
sensitive, but patients who report multiple thyroid symptoms warrant
serum thyroid testing. These results confirm that thyroid dysfunction
is common, may often go undetected, and may be associated with adverse
health outcomes that can be avoided by serum TSH measurement.
For more detail on the The Colorado Thyroid Disease Prevalence
Study
The statistics on thyroid disease in the US also tell a disturbing
tale. Since 1990 SEER cancer statistics show that the overall thyroid
cancer incidence, across all ages and races in the United States, has
been subject to a statistically significant annual increase (1.4 % per
annum). That increase was highest amongst females (1.6 % per annum).
Also worth note is the fact that between 1975 and 1996 the incidence of
thyroid cancer has risen 42.1% in the United States. This increase was
particularly notable in women and most recent figures (1996) show that
the incidence of thyroid cancer has climbed to 8.0 per 100,000.
And what about children? The incidence of soy-formula feeding is
greater in the United States than anywhere else in the world. The
National Cancer Institute (NCI) publication 'Cancer Incidence and
Survival among Children and Adolescents: United States SEER Program'
1975-1995 has reported that the most prevalent carcinomas in US
children and adolescents younger than 20 years were thyroid carcinomas
(35.5%); more prevalent than the more publicised melanomas (30.9%).
Approximately 75% of the thyroid carcinomas occurred in adolescents
aged 15-19 years of age, and NCI note that "the preponderance of
thyroid cancer in females suggest that hormonal factors may mediate
disease occurrence". Hormonal factors includes agents that affect
thyroid hormone status and Soy Online Service believe that soy-formula
use in infancy is an hitherto unrecognised risk factor.
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