Uses
L-Thyroxine sodium salt pentahydrate (Levothyroxine; T4) is a synthetic hormone for the research of hypothyroidism. DIO enzymes convert biologically active thyroid hormone (Triiodothyronine,T3) from L-Thyroxine (T4)[1].
Hazard
A reproductive hazard.
Biochem/physiol Actions
L-Thyroxine (T4) and triiodo-L-thyronine (T3) are iodine-containing hormones produced from thyroglobulin in the thyroid follicular cells. The stimulation of metabolic rate and regulation of growth and development by these hormones appear to be due to their effects on DNA transcription and thus, protein synthesis.
in vivo
Deiodinases (DIOs), which catalyse the conversion of thyroxine (pro-hormone) to the active thyroid hormone, are associated with thyroid stimulating hormone (TSH) levels. DIO1 and DIO2 catalyze activation of thyroid hormone secretion in contrast to DIO3 playing role inactivation of the secretion. Activities of DIO1 and DIO2 play pivotal role in the negative feedback regulation of pituitary TSH secretion[1]. L-Thyroxine (T4) and Triiodothyronine (T3) hormones are known to modulate the expression of ionic channels, pumps and regulatory contractile proteins. Moreover, thyroid hormones have been shown to influence calcium homeostasis and flux responsible for excitation and contractility, with L-Thyroxine and Triiodothyronine modulating its pharmacological control and secretion. In rats fed 12 weeks with the iodine-free diet, a significant decrease in the levels of both Triiodothyronine and L-Thyroxine is observed when compared to the control group fed with standard diet (p<0.001). In the group treated with low doses of L-Thyroxine, an increase in L-Thyroxine levels is observed (p=0.02) while Triiodothyronine levels remain virtually similar to the control group (p=0.19). Rats treated with high doses of L-Thyroxine display a significant increase in both Triiodothyronine and L-Thyroxine circulating concentrations compared to the non-treated hypothyroid group (p<0.001 and p=0.004, respectively) and a significant increase in L-Thyroxine levels when compared to the control values (p=0.03)[2].
IC 50
Human Endogenous Metabolite
Purification Methods
Crystallise the sodium salt from absolute EtOH and dry it for 8hours at 30o/1mm. [Canepa Acta Cryst 4 283 1951, Beilstein 14 II 378, 14 III 1566, 14 IV 2374.]
References
[1] Arici M, et al. Association between genetic polymorphism and levothyroxine bioavailability in hypothyroid patients. Endocr J. 2018 Mar 28;65(3):317-323. DOI:
10.1507/endocrj.EJ17-0162[2] Corriveau S, et al. Levothyroxine treatment generates an abnormal uterine contractility patterns in an in vitro animalmodel. J Clin Transl Endocrinol. 2015 Sep 9;2(4):144-149. DOI:
10.1016/j.jcte.2014.09.005
