Granulosa theca cell tumour in a pregnant mare: concentrations of inhibin and testosterone in serum before and after surgery.

This research discusses a case of a pregnant mare that had a granulosa theca cell tumour (GTCT), as indicated by significantly higher than normal levels of inhibin and testosterone in the mare’s serum. The successful removal of the tumour resulted in a substantial decrease in these hormone levels and the mare’s pregnancy continued healthily.

Case Presentation and Initial Findings

• The research revolves around a 14-year-old Thoroughbred mare that was notably aggressive towards other horses post-breeding. The mare, 73 days into its gestation, exhibited a rapidly enlarging right ovary.
• Upon physical examination and ultrasonography, the researchers determined the mare was maintaining a viable pregnancy, with an enlarged right ovary and a normal-sized left ovary which had corpus luteum present.
• The serum concentrations of inhibin and testosterone in the mare were significantly higher than the normal ranges. However, progesterone was at an average level, indicating the presence of functional luteal tissue.

Diagnosis and Treatment

• Given these findings, the researchers diagnosed the mare with presumptive granulosa theca cell tumour (GTCT), a type of ovarian tumor.
• The researchers then performed surgery on the mare to remove the affected ovary. Post-operation, the histopathological examination of the removed ovary confirmed the presence of a benign GTCT.

Post-Surgical Findings and Pregnancy Confirmation

• The post-surgical measurements at 31-days showed an 18-fold decrease in inhibin and a 10-fold decrease in testosterone in the mare’s serum, indicating the success of the operation in eliminating the tumour.
• The researchers reassessed the mare’s pregnancy at 115 days gestation through rectal palpation and transrectal ultrasonography, confirming the progression of the pregnancy.

Method and Conclusions

• The research confirms that a GTCT is associated with elevated levels of inhibin and testosterone in the serum, a crucial finding for similar future cases.
• It concludes that, in cases where a pregnant mare has ovarian enlargement and shows aggressive behaviour, a GTCT should be considered a possible diagnosis.
• The research also emphasises the usefulness of measuring concentrations of inhibin and testosterone in the mare’s serum to support diagnosing GTCT.