Glucose metabolism in a pony mare with a tumour of the pituitary gland pars intermedia.

The research presents a case study of a pony mare with a pituitary gland tumor. This triggered hyperadrenocorticism in the horse, resulting in symptoms like hirsutism, excessive thirst, persistent hyperglycemia, and general weakness. An unexpected response to insulin and glucose tolerance test, contrasting with a control pony’s reaction, were also documented.

Case of Pituitary Dependent Hyperadrenocorticism

• The research describes a unique case of a horse diagnosed with pituitary dependent hyperadrenocorticism, caused by a tumor in the pars intermedia of the pituitary gland.
• The horse demonstrated several clinical signs of the disease such as hirsutism (abnormal hair growth), polydipsia (increased thirst), and general debility (weakness or frailty).

Hyperglycemia and Insulin Response

• Particularly notable was the horse’s persistent hyperglycemia. Despite the subcutaneous introduction of insulin, the glucose levels in the horse’s body didn’t show any significant changes.
• This response stood in stark contrast to normal biological behavior – commonly, insulin introduction should lead to a drop in glucose levels, as insulin regulates glucose by aiding its absorption into cells.

Cortisol Concentration and Dexamethasone Suppression

• The horse’s resting cortisol values were within normal, despite the presence of the pituitary gland tumor. However, when Dexamethasone (a type of corticosteroid medication) was introduced to suppress cortisol concentration, the duration of the suppression was shorter than what’s considered normal.
• This could suggest that the pituitary gland tumor is affecting the horse’s adrenal response to metabolic stress.

Glucose Tolerance Test

• As part of the research, a glucose tolerance test was carried out. This is typically done to measure how quickly glucose is cleared from the blood.
• Along with glucose, other elements such as cortisol, insulin, and glucagon concentrations were measured during the test.
• The results showed a different response pattern in the subject horse than that in a control pony, reinforcing the conclusion that the pituitary gland tumor affected the horse’s metabolic responses, specifically glucose metabolism.