Studies on the gonadotrophic hormones of pituitary and placental origin
In the early part of this century there was much controversy about the existence nature and number of pituitary gonadotrephins. The era of gonadotrophic studies started when in 1897 Heaps postulated the possible existence of an extra-ovarian factor capable of regulating ovarian activity. His assumption was supported by evidence produced in 1901 by Poa who noted the rapidity of follicular growth in the immature ovary grafted into an adult animal, and by Aschner in 1912 who found that atrophic changes took place in the gonads of dogs after hypophysectomy, Later, in 1924, Evans and hie colleagues reported that in normal rats treated with pituitary extracts enlargement of the ovaries and formation of large numbers of corpora lutea occurred. A few years later Smith (1926) and Smith and Engle (1927), who developed for the first time a satisfactory tecnique of hypophyseotoay in rate, showed that total ablation of the anterior lob- of the pituitary caused profound atrophy of the gonads and accessory genitalia and that this phenomenon could be prevented by the implantation of anterior lobe extracts into the hypophysectomised animal. They further showed that in the immature intact animal, these same implants could induce precocious sexual maturity. Thus, the control and maintenance of gonadal function by the anterior lobe of the pituitary was clearly demonstrated.