The incidence of extracellular thymic cysts in intact and gonadectomized Syrian hamsters, untreated and treated with diethylstilbestrol and steroidal hormones.

Syrian hamsters differ from other experimental animals in many of their responses to the chronic administration of unphysiological amounts of certain steroidal hormones. It is of interest that this is not true of the hamster thymus gland. Thymic cysts are commonly absent or inconspicuous in untreated, gonadectomized or hypophysectomized male and female hamsters prior to 450 days of age. This cystogenicity is rendered markedly precocious following estrogen and androgen administration, given separately or in combination. Progesterone and adrenal cortical hormones have little or no effect. These observations are based upon the study of serial sections of 402 untreated and 1215 steroid-treated hamsters. The results are recorded in detail in one table and seven bar graphs; statistical constants are included.