GROWTH STUDIES

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Abstract
The article presents a summary of studies related to growth, as conducted by the authors during the past 10 yrs. Instead of the names of growth hormone or somatotropic hormone, the term chondrotrophin is preferred. Chondrotrophin is defined as an hypophyseal agent that produces skeletal growth, and that maintains or restores eutrophy of epiphyseal cartilage. Chondrotrophin is assayed by comparison of pre- and post-treatment skiagrams of hypophysectomized rats. The threshold tail growth requirement for determining the unitage was found to be 6 to 7 mms, the spontaneous tail growth following hypophysectomy being between 3 and 4 mm. (a hormonal growth). 0.35 mg. of the authors'' standard acetone dried powder of bovine adenohypophysis produced that effect and was defined as 1 unit of chondrotrophin. The tests were done on rats, weighing 100 g., and hypophysectomized on the day of or one day before the first injn. The extract was given intra-perit. for 7 or 14 days, respectively. The 14-day period of assaying was preferred because 7 days did not permit a distinction between 1 and 2 units. A short chapter (pages 74-78) deals with clinical trials. The results of treatment were judged from total length, tibia skiagrams and dental development in individuals below the age of epiphyseal closure. Chondrotrophin was given in 2 series of 30 subcut. injns. each with one month interval between the 2 series. Ampoules containing 100 I.U. and, occasionally, 1000 I.U. were used. The results were disappointing in general, and the possibilities to explain the failures are discussed. They include different types of dwarfism, inadequacy of total dosage, differences in the threshold dosage of different structures to respond with growth, unsuitability of bovine hypophyses to stimulate human growth, high concn. of poorly active chondrotrophin metabolites with little true chondrotrophin in the extracts, and, finally, the possibility of a synergism between chondrotrophin and other hypophyseal agents in promoting growth in human dwarfism.