Evaluation of Adrenal Cortical Function in Neonatal and Weanling Laboratory Beagle Dogs

The most common target organ for toxicity in the endocrine system is the adrenal gland, and its function is dependent upon the hypothalamus and pituitary gland. Histopathologic examination of the adrenal glands and pituitary gland is routinely performed in toxicity studies. However, the function of the adrenal gland is not routinely assessed in toxicity studies. Assessment of adrenal cortical function may be necessary to determine whether a histopathologic finding in the adrenal cortex results in a functional effect in the test species. As juvenile toxicity studies are more commonly performed in support of pediatric indications for pharmaceuticals, it is important to establish historical control data for adrenal gland function. In this study, adrenal cortical function was assessed in control neonatal and weanling beagle dogs as part of an ongoing juvenile toxicology program. Measurements of serum adrenocorticotropic hormone (ACTH), cortisol prior to and following administration of exogenous ACTH, and aldosterone were conducted beginning at 2 weeks of age continuing through 26 weeks of age. Serum electrolyte concentrations were determined at 4, 13, and 26 weeks of age. Dogs as young as 2 weeks of age synthesize and secrete adrenal cortical hormones and exhibit a functional hypothalamic pituitary adrenal axis.