Hyperandrogenemia and behavioural changes in a mare with equine metabolic syndrome

Summary Hyperandrogenemia and elevated serum anti‐Mullerian hormone (AMH), as well as an increased risk to develop cancer, are well described in women with metabolic syndrome (MS). This case report describes a mare presenting with a 1‐year history of behavioural changes making her unable to be ridden, lack of signs of oestrus, hyperandrogenemia, increased AMH concentration and an enlarged right thyroid gland. Granulosa theca cell tumour (GCT) was suspected by the referring veterinarian due to behavioural changes and inability to work under the saddle, which commonly are associated with GCT in mares. Only mild elevation of AMH levels in the serum, unremarkable findings upon ovarian palpation and ultrasonography made the diagnosis of GCT questionable. At referral in mid‐April, body condition score (BCS) of six out of nine and regional fat deposits were suggestive of equine metabolic syndrome (EMS). Insulin dysregulation (ID) was confirmed by an oral sugar test (OST). A diet considering adequate energy and nutrient intake and exercise regime improved behaviour, work under saddle and insulin levels. Furthermore, the mare showed signs of oestrus again and serum AMH and testosterone were within normal limits. Due to ultrasonographic changes of the thyroid gland, it was excised and thyroid carcinoma confirmed. This case describes the occurrence of EMS, behavioural changes, hyperandrogenemia and concurrent neoplasia in a mare. While there is no proof of a causative link between neoplasia and EMS, the observation of the concurrent pathologies is interesting and warrants further investigation.