Novel thyroid hormones

AbstractThe field of thyroid hormone signaling has grown more complex in recent years. In particular, it has been suggested that some thyroid hormone derivatives, tentatively named “novel thyroid hormones” or “active thyroid hormone metabolites”, may act as independent chemical messengers. They include 3,5-diiodothyronine (T2), 3-iodothyronamine (T1AM), and several iodothyroacetic acids, i.e., 3,5,3’,5’-thyroacetic acid (TA4), 3,5,3’-thyroacetic acid (TA3), and 3 -thyroacetic acid (TA1). We summarize the present knowledge on these compounds, namely their biosynthetic pathways, endogenous levels, molecular targets, and the functional effects elicited in experimental preparations or intact animals after exogenous administration. Their physiological and pathoph ysiological role is discussed, and potential therapeutic applications are outlined. The requirements needed to qualify these substances as chemical messengers must still be validated, although promising evidence has been collected. At present, the best candidate to the role of independent chemical m essenger appears to be T1AM, and its most interesting effects concern metabolism and brain function. The responses elicited in experimental animals have suggested potential therapeutic applications. TA3 has an established role in thyroid hormone resistance syndromes, and is under investigation in Al len–Herndon–Dudley syndrome. Other potential targets are represented by obesity and dyslipidemia (for T2 and T1...

Source: Endocrine - July 19, 2019 Category: Endocrinology Source Type: research