Elevated Testosterone and Progestin Concentrations in a Spayed Female Rabbit with an Adrenal Cortical Adenoma

Abstract

This case was described briefly in a recent book chapter (Lennox AM, Fecteau KA: 2014, Endocrine disease. In: BSAVA Manual of Rabbit Medicine, eds. Meredith A, Lord B, pp 274-276. British Small Animal Veterinary Association, Gloucester, UK). In the previous description, the tumor was described as a pheochromocytoma; however, further evaluation suggested that it more closely resembled an adrenal cortical adenoma. A 10-year-old, spayed female rabbit was presented for a behavior change of 8 months' duration. The rabbit was inappropriately urinating and defecating, as well as demonstrating aggressive behaviors such as chasing, biting, and mounting various objects. The rabbit had elevated progesterone, 17-hydroxyprogesterone, and testosterone concentrations, and ultrasound examination of the abdomen showed a round, homogenous nodule measuring 1.1 × 0.8 × 0.9 cm in the region of the left adrenal gland. Necropsy revealed a unilateral adrenal cortical adenoma. To the authors' knowledge, this is the first complete description of a female rabbit with an adrenal cortical adenoma documented in the literature. Case PresentationA 10-year-old, spayed female rabbit was presented for a behavior change of 8 months' duration. The rabbit was inappropriately urinating and defecating, as well as demonstrating aggressive behaviors such as chasing, biting, and mounting various objects. The rabbit had been spayed in the first year of life.On physical examination, the only significant finding was an enlarged clitoris ( Figure 1). No significant abnormalities were present on either a complete blood count or biochemistry panel. However, the rabbit had elevated blood levels of progesterone (0.63 ng/mL; reference interval for a spayed female rabbit (RISF) 0.09-0.47 ng/mL), 17-OH progesterone (>25.0 ng/mL, extrapolated result 60.2 ng/mL; RISF 0.7-18.9 ng/mL), and testosterone (1.02 ng/mL; RISF 0.02-0.03 ng/mL) [1]. Cortisol (6.2 ng/mL; RISF 4.9-10.1 ng/mL) and androstenedione (1.2 ng/mL; RISF 0.96-4.0 ng/mL) levels were within normal limits [1]. Cortisol, progesterone, and testosterone assays (Coat-a-Count) were from Siemens Medical Solutions Diagnostics, Los Angeles, CA, and 17-OHP and androstenedione assays (ImmunChem Double Antibody) were from MP Biomedicals, Solon, OH.Ultrasound examination of the abdomen showed a round, homogenous nodule measuring 1.1 × 0.8 cm in the region of the left adrenal gland (normal adrenal gland 0.72 × 0.37 cm) [2]; the nodule had an echogenicity approximately equal to the renal cortex. The right adrenal gland was not identified. The remainder of the examination was unremarkable. Due to the combination of clinical signs, elevated sex hormones, and a potential adrenal gland nodule, adrenal cortical disease was suspected. The owner declined exploratory surgery of the abdomen and adrenalectomy; therefore, medical management was recommended to potentially help alleviate clinical signs. Medical management was declined as well.Six months following diagnosis, the patient was presented for progressive difficulty ambulat...

Not Just Uterine Adenocarcinoma—Neoplastic and Non-Neoplastic Masses in Domestic Pet Rabbits (Oryctolagus cuniculus): A Review

“…There were no endocrine tumors in our series. In the literature, adenoma 5 and carcinoma of the adrenal gland 43 were described, the latter after administration of a dye. Hyperplasia of the adrenal gland is reportedly frequent.…”

“…61 Similar to ferrets, lack of feedback inhibition due to spaying has been suspected as possible pathogenesis. 5 Other reported endocrine neoplasms are prolactin-secreting acidophilic adenoma of the pituitary gland, with hyperplasia and neoplasia of the mammary gland, 64,88 as well as teratoma of the pituitary gland, 65 and carcinoma of the thyroid gland. 25…”

Peculiarities of microstructure of the suprarenal glands of rabbits with different types of autonomic tone

“…Significant species peculiarities were determined in the structure of the suprarenal glands of cetaceans (Vuković et al, 2010) and primates (Tachibana et al, 2015;Raharison et al, 2017). Among the studied animals, surveys frequently detected rabbits in which the structure of the suprarenal glands was studied from the perspective of embryogenesis (Sokolov, 1969;Hussein et al, 2015), blood circulation (Kigata & Shibata, 2018), physiological and pathological conditions (Vinson et al, 1985;Baine et al, 2014) and impact of chemical substances (Chandra, 1975;McCreedy & Harmon, 1992). Special attention in morphological studies is paid to the cellular content of the suprarenal glands.…”