Hyperandrogenemia and behavioural changes in a mare with equine metabolic syndrome
Authors: K. Shell, A. Rijkenhuizen, I. Vervuert
Journal: Equine Veterinary Education
Summary
# Editorial Summary Equine metabolic syndrome (EMS) commonly presents with reproductive and behavioural dysfunction, but its concurrent association with neoplasia and hormonal abnormalities has received limited attention in equine medicine. Shell, Rijkenhuizen and Vervuert document a mare initially suspected of having a granulosa theca cell tumour based on behavioural deterioration and work intolerance over 12 months, yet presenting atypically with only mildly elevated anti-Müllerian hormone (AMH) and unremarkable ovarian ultrasound findings. Investigation revealed EMS (body condition score 6/9 with regional adiposity) and insulin dysregulation confirmed via oral sugar testing, whilst concurrent hyperandrogenemia and thyroid enlargement were also identified. Dietary optimisation and exercise programme resulted in substantial improvements: behavioural normalisation, return to work capability, restoration of oestrous cycles, and normalisation of serum AMH and testosterone concentrations, with histopathological diagnosis of thyroid carcinoma following gland excision. Whilst causation remains unproven, the concurrent presentation of EMS, hyperandrogenemia, behavioural pathology and malignancy mirrors recognised patterns in women with metabolic syndrome and suggests that equine professionals should consider systemic metabolic disease as a differential diagnosis in mares presenting with reproductive or behavioural change, rather than defaulting to primary ovarian pathology—particularly when hormonal markers are discordant with clinical suspicion.
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Practical Takeaways
- •When investigating behavioural changes and anestrus in mares, consider equine metabolic syndrome and insulin dysregulation as differential diagnoses alongside ovarian pathology—appropriate dietary and exercise management may resolve both metabolic and behavioural issues
- •Mild or borderline elevations in AMH and equivocal ovarian ultrasound findings should prompt investigation for concurrent systemic conditions (metabolic syndrome, neoplasia) rather than defaulting to granulosa theca cell tumour diagnosis
- •Monitor thyroid gland size during routine examination of mares with metabolic syndrome, as this case suggests a possible association between EMS and thyroid neoplasia that may impact performance and behaviour
Key Findings
- •A single mare with equine metabolic syndrome presented with hyperandrogenemia, elevated AMH, and behavioural changes initially suspected to be from ovarian tumour but confirmed as thyroid carcinoma
- •Dietary and exercise management targeting insulin dysregulation resolved behavioural problems, restored oestrous cycles, and normalized androgen and AMH levels
- •Concurrent equine metabolic syndrome and neoplasia (thyroid carcinoma) were observed in the same individual, suggesting a possible pathophysiological link warranting further investigation