The European Union’s EFSA approved the GMO cotton seeds made by Bayer for food and animal feed.  Scientific Opinion on application (EFSA-GMO-NL-2010-77) for the placing on the market of herbicide-tolerant genetically modified cotton GHB614 × LLCotton25 for food and feed uses, import and processing under Regulation (EC) No 1829/2003 from Bayer CropScience

EFSA European Food Safety Association has approved the use of GMO cotton seeds by Bayer Crop Science for food and animal feed. These seeds have shown to contain very high levels of gossypol. The EFSA does not consider this to be a health issue. Merck disagrees.

http://www.efsa.europa.eu/en/efsajournal/pub/3680.htm

“The observed gossypol levels in cotton GHB614 × LLCotton25 were at the upper limit of ranges reported in literature. The elevated levels of gossypol were considered not to pose concerns for human or animal safety. The EFSA GMO Panel, after considering all the data for cotton GHB614 × LLCotton25 and for the newly expressed proteins 2mEPSPS and PAT, is of the opinion that interactions impacting the food and feed safety of cotton GHB614 × LLCotton25 are unlikely. The EFSA GMO Panel also concludes that cottonseed of GHB614 × LLCotton25 is as nutritious as its conventional counterpart.”

http://www.merckmanuals.com/vet/toxicology/gossypol_poisoning/overview_of_gossypol_poisoning.html

Signs of prolonged excess gossypol exposure in many animals are reduced growth rate, weight loss, weakness, anorexia, and increased susceptibility to stress. Young lambs, goats, and calves may suffer cardiomyopathy and sudden death; if the course is more chronic, they may be depressed, anorectic, and have pronounced dyspnea. Adult dairy cattle may show weakness, depression, anorexia, edema of the brisket, and dyspnea, and also have gastroenteritis, hemoglobinuria, and reproductive problems. In monogastric animals, acute exposure may result in sudden circulatory failure, while subacute exposure may result in pulmonary edema secondary to congestive heart failure; anemia may be another common sequela. Violent dyspnea (“thumping”) is the outstanding clinical sign in pigs. In dogs, gossypol poisoning is primarily reflected by cardiotoxic effects; condition deteriorates progressively, and ascites may be marked. Affected dogs may show polydipsia and have serum electrolyte imbalances, most notably hyperkalemia, with pronounced ECG abnormalities.

I gossypol was tested as a male contraceptive in China it was found to be very effective… but there were side effects…

http://malecontraceptives.org/methods/gossypol.php

The effect of gossypol on human male fertility has been known in China for many years. In 1929, a study of couples who used crude cottonseed oil for cooking showed that they had smaller than average families. Specifically, researchers showed that the oil affected male fertility. Eventually researchers isolated the contraceptive compound gossypol from the cotton seed oil.

This discovery led to large scale testing of gossypol as a male contraceptive in China during the 1970s. The studies involved over 8,000 men, and continued for over a decade. The researchers found that men taking a daily gossypol pill had reliable contraception and no complaints about change in libido. However, the studies revealed two serious flaws: disruption of potassium uptake and incomplete reversibility.

What side effects are expected?

The large-scale trials of gossypol in Chinese men reported an abnormally high rate of hypokalemia among subjects, varying from 1-10%. Hypokalemia is characterized by low levels of potassium in the blood. Potassium is one of the elements used by the muscles and nerves to transmit signals. Symptoms of low blood potassium include fatigue, muscle weakness and at its most extreme, paralysis. Hypokalemia is usually the result of kidney malfunction, and can be caused by excessive consumption of diuretics. Researchers do not understand exactly how gossypol affects the kidneys.