Puberty too soon

MANY girls in the us are starting puberty far earlier than is widely considered normal, according to a recently published report of the first large-scale, multi-racial study conducted by Marcia E Herman-Giddens, professor of maternal and child health at the Chapel Hill School of Public Health, University of North Carolina. Nearly half of the African -Arnerican and 15 per cent of Caucasians girls studied, reached puberty and began developing sexually by the age of eight (Paediatrics, Vol 99, No 4).

This study involved over 17,000 girls in the age-group of three to 12 years, who were seen in 65 paediatric clinics all over the us. About 1,600 of the girls, or 9.6 per cent, were African-American. At the age of eight years, 48.3 per cent of the African-American girls and 14.7 per cent of the Caucasian girls began developing breasts or pubic hair or both. Menstruation started at 12.16 years in the African -American girls on an average and at 12.88 years for Caucasian girls. The average age of menstruation has remained almost unchanged for over 45 years.

This study challenges the textbook timetable of puberty, based on decades old research on British girls. Existing medical guidelines have it that it is abnormal for girls to show the first signs of puberty before the age of eight. As this study shows that a large percentage of American girls have one or both of these characteristics at seven years of age, and in some cases by three years, either the textbooks are outmoded or there are some other, unknown factors. The early onset of puberty was noticed in both the Caucasian and the African-American girls, although there racial differences. were some On an average, the African American girls showed the first signs of sexual maturity about a year earlier than the Caucasian girls.

To understand the implications of these observations, it is important to elaborate on the role of the hormone oestrogen in the human body, particularly in early puberty. Oestrogen is a powerful chemical with its receptors in about 300 different human tissues from the brain to bone to the liver. Its levels begin to rise at the age of about eight. The hypothalamus plays an important part as it spurs the pituitary gland to release hormones, which in turn prompt the ovaries to produce oestrogen. By the age of 11 or 12 years. production of oestrogen and other hormones begins to trigger the development of breasts, growth of the underarm and pubic hair, and the beginning of menstruation.

In addition, these hormones also trigger adolescent features such as oilier hair and blemished skin. In fact oestrogen starts its functions in the pre-natal state. It helps in the formation of the foetus's brain during its early stages of development. It also affects learning ability and memory through later life. Scientists are not very clear as to how oestrogen works in the brain, but its role clearly goes beyond menstruation.

Herman-Giddens and her team wanted to find out whether 'environmental oestrogens', chemicals that mimic oestrogen, are bringing about the early puberty noticed in the American girls. Such a relationship between environmental contamination and sexual abnormality, was noticed in the early 80s by scientists working on alligators. While studying as to how many alligators from Florida's Lake Apopka could be hunted without making the population crash, it was noticed that many of the males had become nearly sterile. Subsequent research showed that thousands of gallons Of DDT-containing pesticide was responsible. This started the study of gender-bending characteristics of pesticides.

Subsequently it was also confirmed that hundreds of chemicals of the postwar age resemble the human sex hormone oestrogen. These include polychlorinated biphenyles, used in the manufacture of electronics, pesticides such as endosulfan and atrazine, polycarbonate plastic found in many baby bottles and water jugs and chlorine compounds that bleach paper. Their molecular structure resembles that of oestrogen, so they influence the same receptors in the body that are sensitive to oestrogen, as the receptors cannot distinguish them. Consequently, the ,oestrogen mimics' can trick the body into turning off, or boosting certain bio-chemical pathways, especially in the reproductive system, disturbing normal development in both sexes.

Though the role of oestrogen like pollutants in diseases like breast cancer and emdometriosis, the painful inflammation of the uterine lining that often causes infertility, has been investigated, there are still no confirmed studies to show that the pollutants can actually switch on the same biological pathways as real oestrogen. Abnormalities in males due to oestrogen mimics, including testicular malformations at birth, have been reported in several countries.

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