Exposure to exogenous estrogen through intake of commercial milk produced from pregnant cows.
BACKGROUND
Modern genetically improved dairy cows continue to lactate throughout almost the entire pregnancy. Therefore, recent commercial cow's milk contains large amounts of estrogens and progesterone. With regard to the exposure of prepubertal children to exogenous estrogens, the authors are particularly concerned about commercial milk produced from pregnant cows. The purpose of the present study was therefore to examine concentrations of serum and urine sex hormones after the intake of cow milk.


METHODS
Subjects were seven men, six prepubertal children, and five women. The men and children drank 600 mL/m(2) of cow milk. Urine samples were collected 1 h before the milk intake and four times every hour after intake. In men the serum samples were obtained before and 15, 30, 45, 60, 90 and 120 min after milk intake. Women drank 500 mL of cow's milk every night for 21 days beginning on the first day of the second menstruation. In three successive menstrual cycles, the day of ovulation was examined using an ovulation checker.


RESULTS
After the intake of cow milk, serum estrone (E1) and progesterone concentrations significantly increased, and serum luteinizing hormone, follicle-stimulating hormone and testosterone significantly decreased in men. Urine concentrations of E1, estradiol, estriol and pregnanediol significantly increased in all adults and children. In four out of five women, ovulation occurred during the milk intake, and the timing of ovulation was similar among the three menstrual cycles.


CONCLUSIONS
The present data on men and children indicate that estrogens in milk were absorbed, and gonadotropin secretion was suppressed, followed by a decrease in testosterone secretion. Sexual maturation of prepubertal children could be affected by the ordinary intake of cow milk.
Maruyama
Kazumi
K
Interdisciplinary Graduate School of Medicine and Engineering, Department of Clinical Nursing and Pediatrics, University of Yamanashi, Yamanashi, Japan.
Oshima
Tomoe
T
Ohyama
Kenji
K
D000818:Animals; D002417:Cattle; D002648:Child; D004967:Estrogens / Q000378:metabolism*; D004970:Estrone / Q000378:metabolism; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D006801:Humans; D007986:Luteinizing Hormone / Q000378:metabolism; D008297:Male; D008892:Milk / Q000009:adverse effects / Q000737:chemistry*; D010060:Ovulation / Q000187:drug effects / Q000378:metabolism; D011247:Pregnancy; D011270:Pregnancy, Animal; D011374:Progesterone / Q000378:metabolism; D012741:Sexual Maturation / Q000187:drug effects / Q000502:physiology; D013739:Testosterone / Q000378:metabolism; D055815:Young Adult
D004967:Estrogens; D004970:Estrone; D013739:Testosterone; D011374:Progesterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone