Forty-nine children with short stature (age range, 4.1-15.9 yr) were examined. Twenty-four (group 1) were submitted twice to an arginine and a sleep test (12-h overnight GH profile). Twenty-five patients (group 2) were submitted twice to an arginine and L-dopa test. Coefficients of variation were calculated between both the results of pharmacological (peak and area under the curve) and sleep tests [mean GH concentration (MGHC), peak, area under the curve, number of peaks above 5 micrograms/L, and peak area]. In group 1 the coefficient of variation of sleep test parameters was significantly lower than that of pharmacological tests (P less than 0.01 to less than 0.001). In the sleep test the area under the curve and MGHC were the most constant parameters. Group 2 showed no difference between the coefficients of variation of the two pharmacological tests. Considering groups 1 and 2 together, the coefficients of variation of the sleep test, in particular the MGHC and area under the curve, were lower than those of the two pharmacological tests. Eight of 24 subjects in group 1 showed a low GH level in 1 series of tests, and a normal level in the other series. Five of 18 subjects in group 2 showed an abnormally low GH response to the arginine and L-dopa tests and a normal response to the 2 repeated tests. Therefore, to prevent an erroneous interpretation of the GH test results, it is very important to perform a sleep test and repeat it whenever GH secretion seems to be deficient or at the lower limits of normalcy.

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. VARIABILIIY OF ARGININE L-DOPA AID SLEEP TEST PERFORMED TYICE I N THE SAME PATIENTS.UP p~rformed arginine and sleep tests (blood ranplrr fro. latter collected every 30' for I2 hours) tuire uithin tuo ueeks in 21 short patients with mean C.A.11.15 years (range 7.5 -15.91 years): 14 males. 7 females; 12 prepybertal, 9 pubertal. Mean height SDS was -2.28 :0.65 ( r -3.85. -1.37); predicted height war 166 ca. for males, 152 cm. for females. Ye calculated X difference betrccn same parameters of double tests (al. a2) according to formula [al-a2/(al+a2)/2! ~100. Results were following: X differences: arginine arginine sleep mean sleep sleep sleep sleep peaks peak (I) area (2) value (3) peak (4) area (5) GH binding sites are recovered in approximately equal proportion in tte mclear and the microsunal frections. In gradient subfrections fran untreated microsms, the GH binding ectivity displays a distrih~tion pettern very similar to that of marker enzymcs for endoy>losnjc reticulum. Iiowever, when digitoniwtrested microsanes are centrifuged to equilibriun, a noticeable proportion of the binding activity un&rps a density shift similar to that of plasma membrane constituents. Solubilization of 8 total particulate frection with Triton X-100, follmd by chrmtography on an hCttaffinity colum, leads to partid purification of the receptor. The abnormally low deep sleep is at minimum a biological marker in these patients. It is possible that the poor GII-secretion in GH-deficient patients is related to a reduction of deep sleep, making the sleep-process triggering the hypothalamo-pituitary GH secretion.6. M a s s a m < M. Maes, JP. Thissen", JM.~e t e l s l e g e r s * University o f Louvain, School o f Medicine, 87 Brussels, Belgium. SEXUAL DIMORPHISM OF HEPATIC GROWTH HORMONE (GH) RECEPTORS I N RATS 18 NOT DUE TO DIFFERENCES I N OCCUPANCY BY ENDOGENOUS GH.To ascertain that t h e sexual dimorphism o f liver G H receptors i n rats i s not d u e to differences i n their occupancy by endogenous GH, specific 125~-bovine GH binding w a s determined on homogenates from male and female animals, before and after MgCIZ treatment t o remove endogenous GH. I n both sexes total and free G H binding increased with a g e (table). In 3 day-old rats free receptors were l o w and increased slightly after MgC12. Until 3 weeks o f age, no sex difference was present. In adult rats, however, female animals had more G H receptors than males, whether endogenous GH w a s removed o r not. In conclusion : 1) i n neonatal rats, t h e l o w G H binding is n o t due to occupancy b y GH; 2) i n adult rats, t h e sexual dimorphism of G H binding i s not d u e to differences i n occupancy b y GH. THE IMPORTANCE OF GROWTH HORMONE (GH) IN THE EPIPHYSEAL CARTILAGE AND BONE CHANGES OF HYPOTHYROILISM (HT).To evaluate the role of GH in the growth retardation of HT, 7-weeks-old female rats were rendered HT by methimazol for 7 weeks (Grl). This resulted in serum T4slpgIdl (ctr 2.4i0.4 vgfdl), growth arrest and 96% depletion of pituitary contents of GH (from 78i3 to...