A synthetic form of thyroxine
L-Thyroxine is a synthetic form of the thyroid hormone thyroxine.1,2,3 In vivo, L-thyroxine (0.9 and 2.7 μg) inhibits synthesis and release of thyrotropin induced by thyrotropin-releasing hormone from the anterior pituitary in mice.1 It also reverses decreases in levels of circulating thymic serum factor (FTS) and the number of T rosette-forming cells in an old age-induced mouse model of hypothyroidism.2,3 Formulations containing L-thyroxine have been used in the treatment of hypothyroidism.
1.Bowers, C.Y., Schally, A.V., Reynolds, G.A., et al.Interactions of L-thyroxine or L-triiodothyronine and thyrotropin-releasing factor on the release and synthesis of thyrotropin from the anterior pituitary gland of miceEndocrinology81(4)741-747(1967) 2.Fabris, N., Muzzioli, M., and Mocchegiani, E.Recovery of age-dependent immunological deterioration in Balb/c mice by short-term treatment with L-thyroxineMech. Ageing Dev.18(4)327-338(1982) 3.Fabris, N., and Mocchegiani, E.Endocrine control of thymic serum factor production in young-adult and old miceCell Immunol.91(2)325-335(1985)
|
Animal experiment: |
Rats[2]Sprague-Dawley female rats (N=22) are used. Non-pregnant rats are divided into four groups: 1) control, 2) hypothyroidism, 3) hypothyroidism treated with low doses of L-Thyroxine (20 μg/kg/day) and 4) with high doses of L-Thyroxine (100 μg/kg/day). Control rats (group 1) are fed with standard diet, while the intervention rats are fed with iodine-free diet for 12 weeks to induce hypothyroidism (groups 2-4) which is continued for four more weeks to allow screening of hypothyroid status and L-Thyroxine-treatment. Food and water (iodine-free diet) are available ad libitum. The hypothyroid group treated with low (group 3) or high doses of L-Thyroxine (group 4) are injected intraperitoneally every 24 h with respectively 20 μg/kg/day and 100 μg/kg/day. Blood samples are collected for thyroid function screening at week 12 and 16 following the initiation of either the control or iodine-free diet. Hysterectomy is performed under general anesthesia (isoflurane 2%) at the end of the treatment and the two uterine horns are placed in physiological Krebs' solution until isometric tension measurements within no more than 1 h. |
|
参考文献: [1]. Arici M, et al. Association between genetic polymorphism and levothyroxine bioavailability in hypothyroid patients. Endocr J. 2018 Jan 11. |
|
动态评分
0.0