Determination of the 24 hour urinary excretion rate of cyclic adenosine 3',5'-monophosphate (cAMP) has become a useful investigative tool in such entities as hyperparathyroidism (Drezner, Neelon, Curtis and Lebovitz 1976;Broadus, Mahaffey, Bartter and Neer 1977; Pak 1980) and hypo-and hyperthyroidism {Guttler, Shaw, Otis andNicoloff 1975). Measurements of cAMP levels in heterogenous groups of adult patients with insulin-dependent diabetes mellitus (IDDM) and noninsulin-dependent diabetes mellitus (NIDDM) yielded variable results, including reduced plasma cAMP (Goldberg, Bohannon, Brooks, Tsalikian, Lorenzi and Forsham 1977), and elevated or normal urinary cAMP (Tucci, Lin and Kopp 1973;Lilienfeld-Toal and Willms 1976). Because of these disparate data, we investigated urinary cAMP excretion in a homogenous group of children with IDDM and in a group of normal children.
Patients and MethodsThe diabetic group (IDDM) consisted of 32 children, ages 7.5 to 18 (mean 13.6) yr (18 males, 14 females). The average duration of diabetes was 5.4 ± 0.7 yr (mean ± SEM). The average daily insulin dosage was 0.93 ± 0.06 u/kg, and the average glycosylated hemoglobin was 12.4% (normal < 8.4%). The control group consisted of 17 children, ages 9.4 to 18.3 (mean 13.6) yr (seven males, ten females). Urinary cAMP, creatinine and glucose were measured in two hour fasting morning specimens. Venous blood was drawn at 0800 h for serum creatinine determination and for thyroxine (T 4 ) and TSH in IDDM only. To avoid the potential problem of age-dependency of urinary cAMP in relation to creatinine excretion and body weight (Kruse and Kracht 1981), results are expressed in terms of glomerular filtration rate (GFR) (Broadus et al. 1977) as well as per mg of creatinine excretion.Urinary cAMP was determined by RIA, using a kit supplied by Becton, Dickinson and Co. (Orangeburg, New York). The intra-and inter-assay coefficients of variation are 9.95% (n = 20) and 9.02% (n = 17). Urinary and serum creatinine were measured by a Gilford System 3500 Analyzer (Gilford instruments, Oberlin, Ohio). Urinary glucose was measured by the glucose oxidase method using a Beckman glucose analyzer (Beckman Instruments, Fullerton, California). Serum T 4 and TSH measurements were performed by routine RIA techniques. Serum iPTH was measured utilizing a carboxyl-terminal antiserum (Hruska, Kopelman, Rutherford, Klahr and Slatopolsky 1975).