During this brief period, hormones regulated their heat cycles to maximize the number and viability of the offspring. These compounds regulated the birth process so that the new kittens would be born when food was most abundant. Because of modern care, our pets live much longer than their ancestors. In their added years these hormones, especially estrogen, can have unwanted or even harmful side effects. Many of these examples are well known.
Reproductive hormones are one of the primary causes of breast cancer in the cat.
Animals that are spayed prior to one year of age may still develop mammary tumors, but the tumors are much more likely to be benign . An OHE would, of course, eliminate any possibility of this occurring. They are not commonly seen cancers in cats but they do occur. Unspayed cats may develop a severe uterine disease called pyometra . With this disorder, bacteria enter the uterus and it becomes filled with pus.