Thyroid hormone concentrations differ between donkeys and horses.

This study aimed to establish normal thyroid hormone levels for donkeys, which had previously been undefined, leading to misdiagnoses. The research showed that thyroid hormone concentrations in donkeys differ significantly from horses, indicating the need for species-specific guidelines regarding thyroid activity in equids.

Objective and Methodology

• The aim of the study was to determine the normal thyroid hormone (TH) levels in healthy, adult donkeys and compare these to the TH levels in horses. The thesis was that reference intervals had not previously been set for donkeys, leading to potential confusion in diagnosing thyroid diseases.
• The research methodology involved testing 38 adult, healthy Andalusian donkeys and 19 healthy Andalusian horses from two neighboring farms. The donkeys were divided into various age and gender groups. The horses used provided a comparison group.
• The five types of TH tested in the animals’ blood were free triiodothyronine (fT3), total triiodothyronine (tT3), reverse triiodothyronine (rT3), free thyroxine (fT4), and total thyroxine (tT4). This was done using a radioimmunoassay, a highly sensitive lab technique for measuring substances in the body.
• The researchers ensured conditions were strictly controlled – the animals received no treatment for 30 days prior to testing, were disease-free, and the samples all collected on the same morning.

Results of the Study

• The study findings indicated that serum TH concentrations were overall higher in donkeys than in horses, leading to the conclusion that the levels of these hormones differ significantly between these two species.
• When focusing on the donkeys, it was found that younger donkeys (less than 5 years old) had higher serum rT3, fT4, and tT4 concentrations as compared to those older than 5 years. In addition, older donkeys (those aged 11 years and more) had lower fT3 and tT3 levels than both groups of younger donkeys.
• However, there was no significant difference found in the TH concentrations with respect to the gender of the donkeys examined.

Conclusions and Implications

• The research concluded that there are significant differences in TH concentration between healthy adult donkeys and horses. This has led to a call for the establishment of species-specific TH reference guidelines for evaluating clinicopathological data in equids, paving the way for more accurate diagnoses of thyroid diseases.
• The researchers also indicated the need for further studies to understand the physiological mechanisms leading to these differences in TH concentrations between the two species.