By Roberta Attanasio
According to the International Programme on Chemical Safety, World Health Organization (WHO) (2002), an endocrine disruptor is an exogenous substance or mixture that alters function(s) of the endocrine system and consequently causes adverse health effects in an intact organism, or its progeny, or (sub) populations.
This year, a group of experts convened by the United Nations Environment Programme (UNEP) and WHO defined the growing impact of hormone disruptors on human health problems a “global threat“.
What is the endocrine system? The endocrine system is one of the communication systems of our body and is found in all mammals, birds, fish, and many other types of living organisms. It’s made up of glands, which are located throughout the body and produce hormones. The major glands are the pineal, pituitary, thyroid and adrenal glands, as well as pancreas, ovaries and testes.
What are hormones? Hormones are chemical messengers that broadcast messages throughout the body. Radio broadcasting stations use radio receivers to reproduce the audio sound signals. Similarly, endocrine messengers must be received through specialized receivers to transmit signals – these specialized receivers are called receptors.
Therefore, in order to respond to a hormone, a cell must bear a receptor specific for that hormone. By interacting with a receptor in or on a cell, the hormone transmits a signal that tells the cell to behave differently – for example to grow more, or to stop growing.
Hormones and the signals they transmit are critical to the normal functioning of every tissue and organ in both vertebrates and invertebrates and are often quite similar across species. There are over 50 different hormones and hormone-related molecules that, from conception through adulthood and into old age, coordinate and regulate all biological processes in the body, including the development and function of the brain and nervous system, the growth and function of the reproductive system, the development and function of the immune system, as well as metabolism and blood sugar levels.
What are endocrine disruptors? Endocrine disruptors (also called endocrine disrupting chemicals) are chemicals that interfere in some way with hormone action and in so doing alter endocrine function and cause adverse effects on the health of humans and animals.
Hormones and endocrine disruptors can act at all times during life – fetal development, infancy, early childhood, puberty, adulthood and old age. However, the strength of their impact may be different depending on the timing of their action.
For example, during adult life the effects of hormones or endocrine disruptors may occur only during exposure. When exposure ends, the effects decrease.
What is developmental programming? Because hormones play an important role in the development of tissues and organs during fetal life, infancy and/or early childhood, exposure to endocrine disruptors during this time may cause permanent effects. This process is called developmental programming and leads to increased susceptibility to diseases later in life.
Some endocrine disruptors produce transgenerational effects – effects that can cross generations. Exposure of a pregnant woman or a pregnant animal may affect not only the development of her offspring but also their offspring over several generations.
What are examples of endocrine disruptors? One well-known example of endocrine disruptors is diethylstilbestrol (DES), a synthetic estrogen. Prior to its ban in the early 1970’s, DES was prescribed to millions of pregnant women to block spontaneous abortion and promote fetal growth. It was later discovered, after the children went through puberty, that DES affects the development of the reproductive system and causes vaginal cancer.
An additional example of endocrine disruptors is bisphenol A (BPA). BPA is a chemical used mostly as a monomer in the production of polycarbonate plastic and epoxy resins. Polycarbonate is widely used in tableware, microwave ovenware, food containers, water bottles, milk and beverage bottles, and water pipes. Epoxy resins are used as protective linings for a variety of canned foods and beverages. Therefore, exposure to BPA occurs primarily through the diet and it has been linked to developmental toxicity for fetuses, infants and children (effects on the brain, behavior and prostate gland). Exposure to BPA has been also linked to the development of obesity, In addition, results from a recent study show that BPA may act as a complete mammary gland carcinogen.