Clinical genetics of defects in thyroid hormone synthesis

Defects of Thyroid Hormone Transport in Serum

Inherited abnormalities of thyroid hormone-binding proteins are not uncommon and can predominate in some ethnic groups. They alter the amount of iodothyronines present in serum and, although the concentration of free hormones remains unaltered, routine measurement can give erroneous results. With a single exception, inherited defects in thyroxine-binding globulin (TBG), are X-chromosome linked ...

Genetic Defects in Thyroid Hormone Supply

INTRODUCTION Congenital hypothyroidism (CH) is the most frequent endocrine-metabolic disease in infancy, with an incidence of about 1/2000-4000 newborns (1,2). With the exception of rare cases due to hypothalamic or pituitary defects, CH is characterized by elevated TSH in response to reduced thyroid hormone levels. In absence of an adequate treatment, CH determines growth retardation, delays i...

Extrathyroidal thyroid hormone synthesis?

A paper published in this issue of the Journal of Endocrinology has revisited the hypothesis that thyroid hormones may be generated by tissues outside the thyroid gland in higher organisms including mammals. This commentary appraises the strengths and weaknesses of the study, the alternative explanations for the findings and possible future measures to investigate further. The concept of extrat...

Thyroid Hormone Synthesis in Thyroglobulin

~-14C]Tyrosine-labeled noniodinated hog thyroglobulin was iodinated enzymatically and nonenzymatically (iodine, iodide-chloramine-T, pH 7.4, or iodine monochloride, p.H 8.1). This led to similar levels of iodine incorporatzon as well as of thyroid hormone synthesis. Iodine monochloride at pH 5.5 formed “hormonogenic” iodotyrosine residues, but no hormone residues. The latter were formed when th...

Thyroid Hormone Synthesis and Secretion