Endocrinological changes before and after removal of the granulosa theca cell tumor (GTCT) affected ovary in 6 mares.

This study investigates hormonal changes in mares (female horses) with a type of ovarian tumor called granulosa theca cell tumor (GTCT) before and after surgical removal of the affected ovary. Results show an abnormal increase in testosterone levels and a decline in other hormones, with testosterone levels normalizing after surgery but other hormone levels remaining consistently low.

Context and Purpose of the Study

• The research was aimed at understanding the endocrinological characteristics or hormone profiles of mares affected by GTCT, a type of ovarian tumour.
• These tumours can disrupt normal hormone production and lead to alteration in the behavioral and reproductive characteristics of mares.

Methods

• The researchers studied 6 mares with GTCT, collecting peripheral plasma samples both before and after the surgical removal of the tumorous ovary.
• They measured the concentrations of six different hormones in the plasma samples, including testosterone (T), follicle stimulating hormone (FSH), luteinizing hormone (LH), immunoreactive-inhibin (ir-INH), progesterone (P) and estradiol-17beta (E(2)). This was done using a technique called radioimmunoassay.

Findings

• Prior to surgery, all the mares displayed significantly higher testosterone levels compared to normal, both in the breeding and non-breeding seasons. Meanwhile, all the other hormone levels were lower.
• After the removal of the affected ovary, testosterone levels decreased, matching that of healthy mares. However, the levels of other hormones remained lower than in unaffected horses.

Interpretation and Implications

• The researchers suggest that the high testosterone levels may stem from abnormal follicles in the ovaries affected by GTCT.
• This heightened testosterone could be due to a lack of aromatase, an enzyme responsible for the conversion of testosterone to estrogen, which is usually inhibited by this kind of tumor.
• The researchers surmise that elevated testosterone is a typical feature of mares with GTCT.
• The study also postulates that these high levels of testosterone could suppress the production of gonadotropins, a group of hormones that includes FSH and LH.
• These findings could have significant implications for the diagnosis and management of GTCT in mares.
• Although surgical removal of the affected ovary can bring testosterone levels back to normal, it might not fully restore the balance of other hormones, suggesting a potential need for additional therapies or interventions after surgery.