Aetiological relevance of haematological, biochemical and endocrine parameters on equine odontoclastic tooth resorption and hypercementosis (EOTRH).

Background: The dental syndrome EOTRH is a painful, progressive dental disease with an unknown aetiology. The often painful nature of EOTRH emphasises the need for a better knowledge of the underlying pathogenic mechanism and risk factors. A comparative analysis of haematological, biochemical and endocrine values in EOTRH-affected and non-affected horses has not been described.

Objectives: To compare haematological, biochemical, and endocrine parameters in EOTRH-affected and non-affected horses to detect risk factors for horses developing EOTRH.

Study design: Cross sectional.

Methods: Blood samples of 154 Icelandic horses aged 15 years and older were collected. A CBC, biochemistry panel, and endocrine profile were performed. A detailed examination of the rostral oral cavity was performed, and incisors were evaluated radiographically using a standardised scoring system. Based on the results, the study population was separated into 'EOTRH-affected' (n = 109) and 'EOTRH-nonaffected' (n = 23) horses. A staging system enabled further differentiation into mild (Stage 2), moderate (Stage 3) or severe (Stage 4) EOTRH-affected versus Stage 0 (EOTRH-nonaffected). To assess the correlations between EOTRH diagnosis and the measured parameters, logistic regression analysis was performed.

Results: No consistent abnormalities were detected in the CBC. In the biochemistry panel, selenium deficiency (38%) and hypovitaminosis D (83%) were the only consistent abnormalities observed across the entire study population. Endocrine analytes showed no abnormalities in thyroid function. Pituitary pars intermedia dysfunction was diagnosed in 17% of the horses.

Main limitations: Irregular distribution of horses between the control group and the EOTRH-affected group. Plasma concentrations were measured only once, and no functional tests of the thyroid gland, nor an oral sugar test or TRH stimulation test were performed.

Conclusions: EOTRH triggers a predominantly local inflammation in the oral cavity, without measurable changes in the inflammatory cells or significant variations in plasma vitamin and trace element serum concentrations.