Hypertestosteronism in an intact female alpaca secondary to an interstitial cell tumor

An apparently healthy, 10 year old female alpaca was presented for infertility and male-like behavior. She had failed to conceive after exposure to intact males (multiple observed breeding) since her last parturition. All female alpacas housed with her were determined to be pregnant. She had been regularly mounting other female alpacas for over 1 year. A month prior to presentation, she had elevated serum testosterone concentrations. Abdominal computed topography (CT) identified a soft tissue (attenuating mass like structure with multiple cystic areas) associated with right uterine horn and right ovary, consistent with a neoplastic process. Bilateral ovariectomy was performed; left ovary was 6 cm in length and had 2 firm nodules (0.9 and 0.8 cm in diameter) and cystic areas were identified in right ovary. Both ovaries were submitted for histopathologic evaluation. Pre and postop blood samples were submitted to endocrine laboratory (University of California, Davis, Davis, CA) for inhibin B, progesterone, and testosterone. Preop blood samples had following concentrations; inhibin βB : 40.1 pg/ml; progesterone: 1.2 ng/ml; and testosterone 1538.3 pg/ml; and postop blood samples had: inhibin βB : 4.9 pg/ml; progesterone: 0.11 ng/ml; and testosterone: 26.4 pg/ml. Blood samples submitted from a healthy intact female alpaca (to provide a reference range for normal values) had following concentrations; inhibin βB : 41.7 pg/ml; progesterone: 0.01 ng/ml; and testosterone: 33.7 pg/ml. Preop hormone concentrations confirmed hypertestosteronemia and its ovarian source was confirmed by postoperation hormone concentrations. Lowering of inhibin β B and progesterone in postop sample was consistent with expected changes that occur following removal of ovaries. Right ovary had multiple cysts lined with attenuated to ciliated cuboidal eosinophilic material and a diagnosis of cystic rete ovarii, whereas left ovary had 2 neoplastic structures composed of packed polygonal cells with indistinct borders and abundant eosinophilic cytoplasm. No mitotic figures observed (10 fields; 400 x magnification) indicating a benign nature of the tumor (interstitial cell tumor). Testosterone produced by left ovary was most likely was responsible for cystic condition of right ovary and cystic rete ovarii. Interstitial or Leydig stromal cell tumors are rare ovarian tumors that belong to sex cord stromal tumors group. These tumors account for < 0.1% of all ovarian tumors in women and are even more rare in camelids. Interstitial cell tumors are characteristically benign and unilateral and produce testosterone. Although interstitial tumors are considered benign neoplastic conditions, they have significant effects on fertility, often ending reproductive life, as in this case. It is important to determine hormone concentrations to diagnose hypertestosteronemiam, followed by histopathology of ovaries in females exhibiting male-like behavior and virilization, to assist in definitive identification of interstitial cell tumors.

Keywords: Camelid, ovary, interstitial cell tumor, Leydig cell, hypertestosteronemia

This manuscript was originally published in the journal Clinical Theriogenology Vol 12(3) Sept 2020.  Clinical Theriogenology is the official journal of the Society for Theriogenology (SFT) and the American College of Theriogenologists (ACT).  This content has been reproduced on the IVIS website with the explicit permission of the SFT/ACT.