Genetic and Environmental Influences on Thyroid Hormone Variation in Mexican Americans

Abstract

Thyroid hormones play major roles in the regulation of a wide range of metabolic and physiologic processes, but the genes and environmental factors that affect normal, quantitative variation in thyroid hormone concentrations are largely unknown. Using quantitative genetic methods, we evaluated the effects of genes and environmental factors on thyroid hormone variation in 586 women and 425 men from 27 randomly ascertained Mexican-American families from the San Antonio Family Heart Study. Data were available on free and total T(4), free and total T(3), TSH, thyroglobulin, and T(4)-binding globulin, as well as on covariates, including sex, age, weight, lifestyle habits, physical activity, and others. These covariates accounted for 2-18% of total phenotypic variation, whereas genes accounted for 26-64% of the variation. Overall, free T(3) had the highest heritability, which is noteworthy because it is the most biologically active thyroid hormone and accounts for the vast majority of metabolic and physiologic effects of thyroid hormones. Our results indicate that genes account for a substantial portion of variation in human thyroid hormone levels, and suggest that further studies to identify the genes involved in this variation could reveal important insights into the processes that govern thyroid-mediated metabolism.

Heredity and lifestyle in the determination of between-subject variation in thyroid hormone levels in euthyroid men

“…Reported estimates range from 32 to 65% for TSH, from 37 to 65% for FT 4 , and from 23 to 67% (7,10,11). The observation of the lowest estimate for TSH is in agreement with observations from Samollow et al (11).…”

“…The physiological basis of the set point of this axis is poorly understood (6). Twin studies demonstrate a moderately strong genetic influence (7,8,9,10,11). In recent years, several of the genes involved in this regulation have been identified, with common genetic variation in phosphodiesterase 8B (PDE8B), TSH receptor (TSHR), deiodinase 1 (DIO1), and capping protein muscle Z-line beta (CAPZB) being associated with circulating THs (12,13,14,15,16,17,18,19,20,21,22).…”

“…Few studies have investigated genetic together with lifestyle-related determinant factors of thyroid function (8,11). This study therefore investigates the contribution of genetics, i.e.…”

The acute myxedema after hyperthyroidism treated by radioactive iodine and its sequelae

“…Populacione studije su pokazale da je serumska koncentracija FT3 parametar koji ima najve u interindividualnu varijabilnost od svih laboratorijskih parametara tireoidne funkcije (20). Trijodtironin ima osoben cirkadijalni ritam koji sa izvesnom vremenskom zadrškom prati cirkadijalni ritam TSH, što ukazuje na njegovo tireoidno poreklo i veliki  ziološki zna aj (21).…”

Cognitive Function in Elderly with Subclinical Hypothyroidism

“…The prevalence estimates have varied depending on the population studied and the criteria used to define it. Besides age and gender, genetics is among the population factors that inflict variation to prevalence estimates, accounting for almost 65% thyroidal phenotype [Samollow et al 2004, Peeters RP 2009. Also, the amount of dietary iodine has to be considered.…”