Progesterone regulates hypothalamic-pituitary-thyroid axis

Progesterone is a natural steroid hormone excreted by animals and humans, which has been frequently detected in the aquatic ecosystems. The effects of the residual progesterone on fish are unclear. In this study, we aimed to examine the effects of progesterone on the hypothalamic-pituitary-thyroid (HPT) axis by detecting the gene transcriptional expression levels. Zebrafish embryos were treated with different concentrations of progesterone from 12 hours post-fertilization (hpf) to 120 hpf. Total mRNA was extracted and the transcriptional profiles of genes involved in HPT axis were examined using qPCR. The genes related to thyroid hormone metabolism and thyroid hormone synthesis were up-regulated in zebrafish exposed to progesterone. These results indicated that progesterone affected the mRNA expression of genes involved in the HPT axis, which might interrupt the endocrine system in zebrafish. Our data also suggested that zebrafish is a useful tool for evaluating the effects of chemicals on the thyroid endocrine system.