Ask Linsey

By Linsey McLean

This column will be a regular feature in Natural Horse. Your questions are invited.

Q: My pregnant mare has edema from the udder to the front legs. What causes this?

A: This edema is characteristic of toxemia of pregnancy caused by underlying hypothyroidism. A blood test may or may not tell the whole story. You may get lucky and have it show. Most of the time, however, it will not, as it is an autoimmune condition caused by high levels of sex binding globulins binding thyroid, in turn, caused by the high levels of estrogens of pregnancy. We don't have the same testing available for horses as we do for humans. Usually older mares are more susceptible, and the problem is compounded by environmental exposure to pollution, as many pollutants act as xenoestrogens in the body. This, biochemically, manifests as the effects of too much estrogen in the body.

This happens frequently to people too, and I have personally experienced that. Most affected females have underlying autoimmune thyroid disease that was present in lowered levels even before the pregnancy. Thyroid supplementation beginning at very low dosages of the totally natural kind, should help dramatically, as will B6, zinc, calcium, magnesium, high protein diet, and canola oil. Since the EPM/EPDS/Environmental Illness program addresses the thyroid connection, this program would be helpful here too.

Linsey McLean, biochemist, is the founder and CEO of Vita Royal Products, Inc. She is a graduate of the University of Michigan with specialties in Biology, Chemistry and Clinical Microbiology. Linsey has been granted several U.S. Patents and has been honored with prestigious awards. In 1983 and 1984, Vita Royal was chosen as official supplier for the U.S. Equestrian team. Both custom and commercial supplements were formulated for the Olympic team which, incidentally, won a record number of gold and silver medals. She is also, of course, a horse owner.

Please send in your questions to or call 800-660-8923.