Age-related Qualitative Histological and Quantitative Stereological Changes in the Equine Pituitary.

The research article focuses on understanding how changes in the pituitary glands of horses relate to their age and its link to the occurrence of a disease identified as pituitary pars intermedia dysfunction (PPID). The study analyzes several variables such as weight, volume, cell size and cell number in the pituitary glands of 124 horses and draws comparisons between PPID-associated and non-PPID-associated conditions.

Summary of Methods

• The study engaged a cohort study of 124 horses whose pituitary glands were examined post-mortem at the Institute of Veterinary Pathology, Ludwig Maximilians University Munich, between 2008 and 2012.
• The researchers analyzed the weight and histological structure of the pituitary glands and divided them into sections of around 2mm each for detailed analysis.
• A grading scheme was used to evaluate morphological alterations in the pars intermedia (PI), a part of the pituitary gland.
• The study also looked at the volume fractions and total volumes of the three pituitary lobes – PI, pars distalis (PD), and pars nervosa (PN).
• They calculated the total number and average size of pituitary interstitial cells (PIC).

Key Findings

• Pituitary weight, PI volume, total number, and mean volume of PIC showed an increase with age in all horses.
• An association was found between groups based on histological changes, the emergence of PI adenomas, follicles and cysts in the PI, lipofuscin in the PN, and increased age.
• However, the same association was not identified in terms of changes in the PD, invasion of basophil cells into the PN, or the occurrence of hemorrhage and necrosis.
• 18% of the horses had PI adenomas, a type of tumor in the PI region. However, only 3% of horses were visibly suffering from PPID, implying that most PI adenomas were incidental and non-functional.
• The total PI volume and the number of PICs in horses with PPID-associated PI adenomas were significantly higher, while the average size of PICs was smaller. This indicates that different growth mechanisms might lead to adenoma formation.

Implications and Conclusion

• Results indicate that age-related changes in the pituitary gland can be linked to the occurrence of non-PPID related adenomas (tumors) in horses.
• The findings suggest that quantitative stereological methods can be used for the post-mortem diagnosis of PPID in horses, affirming the connection between pituitary weight and the manifestation of PIC hyperplasia.
• This study nuances our understanding of the clinical manifestations of PPID and could influence the approach to diagnosing and treating equine endocrine diseases.