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  • Title: Calcium oxalate crystal growth in normal urine: role of contraceptive hormones.
    Author: Tawashi R, Cousineau M, Denis G.
    Journal: Urol Res; 1984; 12(1):7-9. PubMed ID: 6719658.
    Abstract:
    Oral contraceptives inhibited the growth of calcium oxalate crystals in female urine, and the growth rate inhibition depended on the dose of ethinyl-oestradiol in the oral contraceptive agent. The results suggest that the crystallization kinetics of calcium oxalate in urine could be under the control of oestrogenic hormones by an unidentified mechanism. The crystallization kinetics of calcium oxalate was studied in the urine of males, females, and females on oral contraceptives (OCs), for the determination of the crystal growth rate under defined experimental conditions that could offer possible clues as to the role of estrogenic hormones in calcification. 49 subjects on an uncontrolled diet participated. 12 female subjects received OCs as combination tablets containing 0.03 mg or 0.05 mg ethinyl estradiol with 1 mg progestin. The urine sample was taken before lunch. Total calcium concentration and pH were determined immediately for each urine sample. All samples were within the normal physiological limits and in accordance with the recently reported circadian rhythm for normal subjects at this period of the day. There was no significant difference between the median volume diameter D50 of calcium oxalate crystals grown in the urine of males and in the urine of females. There was a significant difference (PL 0.05) between the median diameter of the crystals grown in the urine of females on OCs and controls. The determination of the uniformity factor that provides a measure of the uniformity of distribution indicates that the size distribution of the crystals has not been affected by estrogenic hormones. The calcium oxalate crystal growth rate in the urine of females was not significantly different from that obtained in the urine of the male. The relatively higher coefficient of variation for the female group (68.8%) versus the male group (42%) could be attributed to the variations in the concentration of urinary excreted estrogens during the different phases of the menstruation cycle, but the intake of OCs produced a remarkable and significant retardation of the growth rate of calcium oxalate crystals in the urine of female subjects. Growth inhibition increased with an increase in the dose of the estrogenic hormone in the OC tablet. The 0.05 mg ethinyl estradiol tablet exerted a higher inhibitory effect than the 0.03 mg dose. On the basis of these preliminary results, one can speculate that estrogen hormones and/or their metabolites may play a key role in the formation of calcium oxalate crystals in the urinary tract.
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