Abundance of Anti-Muellerian hormone in cat ovaries and correlation of its plasma concentration with animal age, weight and stage of the estrous cycle.

In female animals of different species, Anti-Müllerian hormone (AMH) is produced by follicular granulosa cells and has been associated with the ovarian follicle pool. Because concentration of AMH in plasma of ovary-intact female cats is apparently more variable than previously assumed, we have analysed AMH concentration in blood of cats (n = 93) presented for routine ovariectomy and assessed ovarian histology and AMH protein expression in the surgically removed ovaries. We hypothesised that AMH is synthesized only in preantral and small antral follicles and that plasma AMH concentration reflects the antral follicle count (AFC). Corpora lutea were detected in 35% of the female cats, whereas plasma progesterone concentration was ≥1 ng/mL in 57% of the cats. Follicular cysts were present in 15 cats (16%). Positive immunostaining for AMH protein was detected in close to all primordial and antral follicles, ovarian cysts, 70% of corpora lutea and 28% of atretic follicles. Concentration of AMH in plasma averaged 6.8 ± 0.5 ng/mL (range 1.3-21.7 ng/mL). The AFC increased with increasing AMH concentration with a moderate positive correlation between AFC and AMH (r = 0.286, p < 0.01). Plasma AMH concentration was not affected by season or cats' age, weight, stage of the estrous cycle and presence of follicular cysts. In conclusion, AMH protein is expressed in all endocrine structures of the cat ovary. While AMH is a marker for the presence of ovarian tissue, its usefulness to assess ovarian function in individual female cats is of limited value.