The first international standard for human urinary FSH and for human urinary LH (ICSH), for bioassay.

This paper describes the preparation and nature of the First International Standard for Human Urinary Follicle Stimulating Hormone and for Human Urinary Luteinizing Hormone, for Bioassay, and of two batches of working standard which were prepared from the same material. A collaborative study of these materials was carried out by six laboratories in six different countries. The FSH and LH activities of the Standard were assayed in terms of those of the Second International Reference Preparation of Human Menopausal Gonadotrophins, Urinary, for Bioassay, which it replaces. The results from 20 valid FSH assays and 30 valid LH assays (using four different methods) obtained in this way gave a weighted combined potency estimate for FSH of 53.7 IU, with 95 % fiducial limits of 47.2-61.1 IU, and for LH of 46.2 IU, with 95 % fiducial limits of 43.3-49.3 IU. Accelerated degradation studies of the Standard stored at elevated temperatures suggested that the stability of both FSH and LH activities under normal storage conditions would be satisfactory. The FSH and LH activities of the two batches of working standard (WS-A and WS-B) were compared with those of the Standard and were not found to differ significantly, except for the LH activity of WS-B which appeared to be slightly higher than that of the Standard. Accelerated degradation studies did not show any significant differences in stability between the Standard and batches of working standards. On the basis of these results the Standard has been established by WHO and allocated a potency for FSH of 54 IU per ampoule and for LH 46 IU per ampoule. The International Units for FSH, Human Urinary, for Bioassay and for LH (ICSH), Human Urinary, for Bioassay are thus defined as the activities contained in 0.1138 mg and 0.13369 mg of the International Standard, respectively.