Adrenal cortex stimulation with hCG in spayed female dogs with Cushing’s syndrome: Is the LH-dependent variant possible?

Abstract

Background: The expression and overexpression of luteinizing hormone receptors in the canine adrenal gland cortex has been reported. Therefore, it was hypothesized that a luteinizing hormone (LH)-dependent form of Cushing's syndrome (CS) could exist in dogs. Aim: Assess whether the adrenal gland post ovariectomy exhibits a greater response to ACTH stimulation. Evaluate whether the adrenal gland responds to hCG stimulation by increasing the release of cortisol. Consider whether hCG stimulus testing would be useful as a diagnosis for possible cases of LH-dependent Cushing’s syndrome Methods: Cortisol concentrations were measured from healthy female dogs (n=16) at baseline and following ACTH stimulation before and two months after gonadectomy (OVx). Cortisol concentrations were also measured from female dogs with CS (n=14) following administration of hCG (5000 IU). A post-hCG cortisol concentration of greater than140 nmol/L was used to define dogs with LH-dependent Cushing's syndrome. Results: In normal female dogs, both pre-and post-stimulation cortisol concentrations increased following OVx (P=0.002 and P=0.0003, respectively). In female dogs with CS, cortisol concentrations increased following stimulation with hCG in 57% (8/14; P=0.002). Age at the time of OVx was associated (P=0.015) with the cortisol response to hCG (8 [5-9] years vs. 3.5 [2-6] years, P=0.0013). Conclusion: Based on these results, an LH-dependent form of CS occurs in spayed female dogs, and that it is more likely to occur when female dogs are spayed later in life.

Keywords

• aberrant receptors
• cushing's syndrome
• gonadectomy
• hcg
• luteinizing hormone