Potent thyrotropic activity of human chorionic gonadotropin variants in terms of 125I incorporation and de novo synthesized thyroid hormone release in human thyroid follicles.

• DOI: 10.1210/jcem.80.2.7852507
• Publication Date: 2014-01-08T16:58:47Z
• Authors: K Yamazaki; K Sato; K Shizume; Y Kanaji; Y Ito; T Obara; T Nakagawa; T Koizumi; R Nishimura
• Keywords: Human chorionic gonadotropin

Using a highly sensitive bioassay for TSH, in which human thyroid follicles incorporate 125I and release de novo synthesized hormone into the culture medium, thyrotropic activities of various hCG preparations were studied. Under conditions employed, bovine TSH (bTSH) was approximately 6- to 9-fold more active than (hTSH). Highly purified prepared from urine normal pregnant women (CR 127) had only trivial activity equipotent 0.00022 microU bTSH/U or 0.0013 hTSH/U (19.7 hTSH/mg hCG). Hybrid (AB1ER) also elicited low (14.0 hTSH/mg), whereas crude moderate (0.041 hTSH microU/U 127 microU/mg protein). Deglycosylated hCG, very weak LH/hCG receptor agonist, most potent agonist (588 hCGs patients with trophoblastic tumors greater TSH-like (37-84 protein) hCG. Asialo-hCG patient choriocarcinoma (468 hTSH/mg). Submaximal doses bTSH variants produced additive stimulation function. Furthermore, effect inhibited by anti-TSH antibody obtained myxedema. These vitro findings suggest that although is reported exert cAMP-stimulating on rat thyroid-like cells (FRTL-5) Chinese hamster ovary transfected complementary DNA (0.092-0.72 hCG), induced authentic too cause hyperthyroidism pregnancy. However, some tumors, particularly asialo-hCG, has sufficient clinically overt when excessively.