Sex steroids in animals absent gonads: A case series

Identifying possible sources of sex steroids is challenging in animals exhibiting apparent responses in reproductive tissues but presenting with a history of having been neutered. Sex steroids, typically secreted by the gonads, also induce responses in non-reproductive tissues including the skin or brain, sometimes affecting behaviors. The analysis of hormones has become a mainstay of diagnostic endocrinology in small and large animal practice. The repertoire of those with reproductive relevance has expanded significantly with specific immunoassays detecting anti-Müllerian hormone (AMH) from either ovarian granulosa or testicular Sertoli cells. This has proven to be extremely useful differentiating neutered animals from those that are not. When AMH is undetectable, indicating neutered status, the possibility of sex steroid secretion by non-gonadal, pathological tissue, or other exogenous sources becomes very real. Reported gonadal status (as stated by owners) is not always reliable given that changes of ownership are common, and neutering is not always complete, complicating initial diagnosis. The cases reported here include several that are unique in either their presentation, diagnostic approach or likely etiologic origin. All were submitted primarily for an assessment of their gonadal status. Collectively, they illustrate, with unusual insight, the utility of AMH as a gonadal biomarker, while obviating the complexity of interpretation of reproductive hormone analyses in supposedly gonadectomized cats, horses and dogs manifesting a variety of apparent, reproductive conditions and pathologies.