Removal of the ovaries eliminates secretion of the hormones estrogen and progesterone. Removal of the testes eliminates secretion of the hormone testosterone. Elimination of these hormones obviously leads to decreases in behaviors and physical changes associated with their secretion, such as heat behavior, swelling of the vulva, and estrous bleeding in bitches, and mounting and roaming in dogs. However, reproductive hormones have effects on other tissues in the body and removal of those hormones may inadvertently impact those systems negatively. Other, less obvious, hormone changes also occur after gonadectomy, including persistent elevation in hormones that control the secretion of estrogen, progesterone, and testosterone. Whether these other hormone changes affect other systems positively or negatively often is unclear.
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