254 G. F. Mazzuoli, L. Terrenato 



These interpretations still do not fully explain how this substance, which fluctu- 

 ates in level over very short periods (half life in plasma being 20 — 30 minutes) and 

 is influenced by food intake and starvation, controls growth rate. 



Mitotic rates, as is well known, are higher at night than during the day. The high 

 night-time secretion may, therefore, be more intimately related to growth than to the 

 stabilization of the supply of energy substrate. 



Two final points require emphasis. As the plasma levels of growth hormone 

 fluctuate widely and rapidly a single or even a limited number of samples cannot 

 give an adequate picture of the "growth hormone status" of an individual. Secondly 

 the hormone influences several functions and many tissues in the body; its therapeutic 

 administration to produce a single effect should be undertaken with caution. 



References 



Greulich, W. W., and S. I. Pyle: Radiographic Atlas of Skeletal Development of the Hand 

 and Wrist. Stanford: Stanford University Press. London: Oxford University Press 1959. 



Hunter, W. M., J. A. R. Friend, and J. A. Strong: (in press). 



— , and F. C. Greenwood: A radio-immuno-electrophoretic assay for human growth hor- 

 mone. Biochem. J. 91, 43 (1964). 



Koskinen, E. V. S.: Clinical and metabolic effects of hormonal treatment in bone repair. 

 In Calcified Tissues. Richelle, L. J., and M. J. Dallemagne (eds.). Liege: Universite de 

 Liege 1965, p. 157. 



KosTYO, J. L., and F. L. Engel: In vitro effects of growth hormone and corticotrophin pre- 

 parations on amino acid transport by isolated rat diaphragma. Endocrinology 67, 708 (1960). 



Peckham, W. D., and E. Knobil: Amino acid concentration by the rat diaphragm in 

 response to injury and some metabolic inhibitors. Biochim. biophys. Acta 63, 207 (1962). 



Raben, M. S., and C. H. Hollenberg: Effect of growth hormone on plasma fatty acids. 

 J. clin. Invest. 38, 48 (1959). 



RiGAL, W. M.: The use of tritiated thymidine in studies of chondrogenesis. In Radioisotopes 

 and Bone. McLean, F. C, P. Lacroix, and A. M. Budy (eds.).: Oxford: Blackwell Scien- 

 tific Publications 1962, p. 197. 



— Sites of action of growth hormone in cartilage. Proc. Soc. exp. Biol. 117, 794 (1964). 



Tanner, J. M.: Growth at adolescence. In The Development of Reproductive Systems, 

 II Edition: Oxford: Blackwell Scientific Publications 1962, Chapter 2. 



Intestinal Absorption and Skeletal Dynamic of Calcium 

 in Acromegaly 



G. F. Mazzuoli, L. Terrenato 

 Istituto di Patologia Medica dell'Universita di Roma, Roma, Italia 



Intestinal calcium absorption in acromegaly has been investigated by a com- 

 bination of balance and isotope techniques and calcium absorption has been correlated 

 with other parameters of calcium metabolism. Moreover, calcium balance data from 

 our own and other studies in acromegalic patients have been statistically evaluated. 



Materials and methods 



The study was performed on six acromegalic patients, aged 19 to 51 years, main- 

 tained on a constant calcium and phosphorus diet. Four patients received approxi- 

 mately 450 mg Ca and 1000 mg P, one 200 mg Ca and 800 mg P, and one 750 mg Ca 

 and 1200 mg P daily. All patients were maintained on the specified diets for 8 to 

 10 days before the balance and kinetic studies were started. Metabolic periods (lasting 



