Normally, complex interactive systems of hormones, proteins, genes, and electronic signals relay messages within cells, between cells, and among organs and body systems. These intricate communication highways control every aspect of life: development, growth, behavior, maintenance, reproduction, and aging.
As few as one or as many as hundreds of steps, or interactions, convey these life-sustaining instructions. Interference at any juncture may alter the signal - and the message - and change the final outcome.
A growing body of research shows that EDCs can interfere in any number of places along the signaling routes, or pathways, that start and stop steroid and thyroid hormonal actions. They can act directly to initiate or block a signal or indirectly by influencing production, transport, and break down of hormones and other messengers.
More is known about how synthetic and plant chemicals interact with steroid hormone and thyroid hormone signals than with the other systems. Steroid hormones - including estrogens, androgens, progestins, glucocorticoids, and mineralocorticoids - control reproduction, metabolism, and ion balance in vertebrates. Thyroid hormones thyroxin and triiodothyronine are essential to lifetime growth, development, and tissue maintenance.
Less is understood about how EDCs may interfere with insulin and other peptide hormones, which help regulate metabolism, lactation, growth, and reproduction. Metals, such as cadmium and some organotin compounds, can affect peptide hormone levels resulting in abnormal signaling.
The most studied interactions involve the steroid hormones and thyroid hormones molecular “machinery” found in the bloodstream and in cells. EDCs influence many of these essential molecular components, including hormone receptors, hormone carrying proteins, signal relaying enzymes, and others. |