If you have problems getting an endocrinologist to accept that you just might need a microgram or two of liothyronine, just imagine a future in which there are many more thyroid hormones (and related substances) that have potential!
They do rather make it sound as if thyroid hormone signalling itself has become more complex. When, of course, it is our understanding that developed. The signalling was always appallingly over-simplified.
I wonder if we will be told we still only need levothyroxine because all the other substances can and will be converted in precisely the right amounts in our bodies if our TSH is right?
Endocrine. 2019 Jul 20. doi: 10.1007/s12020-019-02018-4. [Epub ahead of print]
Novel thyroid hormones.
Zucchi R1, Rutigliano G2, Saponaro F3.
Author information
1 Department of Pathology, Laboratory of Biochemistry, University of Pisa, Via Roma 55, Pisa, 56126, Italy. riccardo.zucchi@med.unipi.it.
2 Scuola Superiore Sant'Anna, Pisa, Italy.
3 Department of Pathology, Laboratory of Biochemistry, University of Pisa, Via Roma 55, Pisa, 56126, Italy.
Abstract
The 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 pathophysiological 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 messenger 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 Allen-Herndon-Dudley syndrome. Other potential targets are represented by obesity and dyslipidemia (for T2 and T1AM); dementia and degenerative brain disease (for T1AM and TA1); cancer (for T1AM and TA4). Another intriguing and unexplored question is the potential relevance of these metabolites in the clinical picture of hypothyroidism and in the response to replacement therapy.
KEYWORDS:
Deiodinases; Thyroacetic acids; Thyroid hormones; Thyronamines
PMID: 31327156
DOI: 10.1007/s12020-019-02018-4
