Synthetic progestin norethindrone (NET) widely used in oral contraceptives, hormonal therapy and livestock farming has been detected in various aquatic ecosystems. Recent studies have shown that NET can cause thyroid endocrine disruption in amphibians. However, studies are still lacking on thyroid axis of fish. In the present study, we investigated thyroid hormone levels (T3 and T4) and transcriptional patterns of 15 genes of the hypothalamic-pituitary-thyroid axis (HPT axis) in adult zebrafish that were exposed to solvent control and three measured concentrations of NET (7, 84 and 810 ng/L) for 90 days. The results indicated that NET significantly lowered T3 and T4 levels in both female and male zebrafish. Transcriptional expression profiles of some of the HPT-axis related genes were disrupted. Specifically, the expression levels of tshb and pax8 have increased significantly while dio2 and ugt1ab have decreased in females. In male, however, tshb expression levels were increased while ttr, ugt1ab, thra and thrb were decreased. The overall results demonstrate that NET disrupts thyroid endocrine system by interfering at multiple sites along HPT axis in adult zebrafish.

已在各种水生生态系统中发现了广泛用于口服避孕药，激素疗法和畜牧业的合成孕激素炔诺酮（NET）。最近的研究表明，NET可以引起两栖动物的甲状腺内分泌干扰。但是，关于鱼的甲状腺轴仍缺乏研究。在本研究中，我们调查了成年斑马鱼的甲状腺激素水平（T3和T4）和下丘脑-垂体-甲状腺轴（HPT轴）的15个基因的转录模式，这些基因暴露于溶剂控制下并且测量了三种浓度的NET（7 ，84和810 ng / L），持续90天。结果表明，NET显着降低了雌性和雄性斑马鱼的T3和T4水平。一些HPT轴相关基因的转录表达谱被破坏。具体来说，女性中tshb和pax8显着增加，而dio2和ugt1ab减少。然而，在男性中，tshb表达水平升高，而ttr，ugt1ab，thra和thrb降低。总体结果表明，NET通过在成年斑马鱼的HPT轴上的多个位置进行干扰来破坏甲状腺内分泌系统。