Thyroid hormone transport

Fujiwara, K., et al. Identification of thyroid hormone transporters in humans different molecules are involved in a tissue-specific manner. Endocrinology 2001, 342, 2005-2012. 

Transport of thyroid hormones Transport of vitamin A Osmotic regulation of plasma Non-specific carrier... 

Alteration of thyroid hormone transport and serum total T 3 and T4 levels, but usually no modification of FT 4 or TSH ... 

Polybrominated Diphenyl Ethers. Results of in vitro estrogen receptor and thyroid hormone transport protein binding assays and in vivo studies of thyroid hormone homeostasis indicate that PBDEs have the potential to disrupt normal endocrine function. 

Fujiwara K, Adachi H, Nishio T, Unno M, Tokui T, Okabe M, Onogawa T, Suzuki T, Asano N, Tanemoto M, Seki M, Shiiba K, Suzuki M, Rondo Y, Nunoki K, Shimose-gawa T, Iinuma K, Ito S, Matsuno S, Abe T (2001) Identification of thyroid hormone transporters in humans different molecules are involved in a tissue-specific manner. Endocrinology 142, 2005—2012. 

Reduced synthesis of proteins in the liver can also affect the end omnium. Thyroxine-binding globulin (TBG), the major thyroid hormone transport protein, has been found to be transiently but marisedly decreased during I-ASP therapy [129,130]. In extended observations Ferster et al. [131] demonstrated a decrease of total T4, FT4, total T3, and TBG during induction therapy. The changes in T4... 

Stockigt JR. Chapter 18 Serum thyrotropin and thyroid hormone measurements and assessment of thyroid hormone transport. In Braverman LE, Utiger RD, eds. Werner and Ingbar s the thyroid. 7th ed. Philadelphia Lippincott-Raven, 1996 377-96. 

Friesema, E.C., Docter, R., Moerings, E.P., Stieger, B., Hagenbuch, B., Meier, P.J., Krenning, E.P., Hennemann, G. and Visser, T.J. (1999) Identification of thyroid hormone transporters. Biochemical and Biophysical Research Communications,... 

Zhou, Y., Samson, M., Osty, J., Francon, J., and Blondeau, J. P, Evidence for a close link between the thyroid hormone transport system and the aromatic amino acid transport system T in erythrocytes, ]. Biol. Chem., 265(28], 17000, 1990. 

B17. Braverman, L. E., Foster, A. E., and Ingbar, S. H., Thyroid hormone transport in the serum of patients with thyrotoxic Graves disease before and after treatment. J. Clin. Invest. 47, 1349-1357 (1968). 

Friesema, E. C. et al. 1999. Identification of thyroid hormone transporters. Biochemical and Biophysical Research Communications 254 497-501. 

Friesema, E. C., J. Jansen, C. MUici, and T. J. Visser. 2005. Thyroid hormone transporters. Vitamins and Hormones 70 137-167. 

Table 34.1 Plasma Proteins Involved in Thyroid Hormone Transport Binding of T4 Binding of T3 ...

T3 resin uptake (T3RU). The T3 resin uptake test measures the amount of unsaturated binding sites on the thyroid hormone transport proteins. A proportion of the labeled T3 will bind to available sites on the serum TBG any excess will bind to the resin. Resin uptake is inversely proportional to the number of vacant binding sites and, therefore, inversely proportional to the total TBG. 

THYROID HORMONE TRANSPORT FROM BLOOD INTO BRAIN CELLS... 

The phenomenon of thyroid hormone transport encompasses a number of sequential steps beginning with their secretion by the thyroid follicles and ending with their distribution to multiple sites of metabolism and action within virtually all the body s organs. These steps include equilibration with multiple carrier proteins in the plasma, transcapillary passage of both the hormones and the carrier proteins into extravas-cular spaces, entry into cells through their external membranes, and translocation to subcellular compartments and organelles. Some that are the subject of current inquiry or controversy, include the interaction of the hormones with "minor" transport protein in plasma, the kinetics of transcapillary movement, the presence of specific receptors for the carrier proteins and the hormones on endothelial and epithelial cell membranes, and specific transport mechanisms within cell organelles. 

This report has briefly summarized what we now know about thyroid hormone transport to the central nervous system. The data are still sketchy and much remains to be done. Obviously the brain is a complex organ and major differences in thyroid hormone transport and metabolism are to be expected in its constituent parts, so study of different brain regions as well as different cell types is required. We also need to distinguish between findings in the mature brain and those during fetal and postnatal development. Thyroid hormones play a very different role in these stages of the organism, and possible variations in hormone delivery to cells may contribute to these differences. Finally, in the malnutrition that often accompanies iodine deficiency, we need to ask whether PA synthesis in the choroid plexus is compromised, as it is in the liver. If so, important effects in thyroid hormone delivery to the brain may be expected. 

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