Development of
follicular cysts is a frequent ovarian dysfunction in cattle. Functional changes that precede
cyst formation are unknown, but a role for anti-Müllerian
hormone (AMH) in the development of
follicular cysts has been suggested in humans. This study aimed to characterize intrafollicular
steroids and AMH during follicular growth in a strain of beef cows exhibiting a high incidence of occurrence of
follicular cysts. Normal follicular growth and
cyst development were assessed by ovarian ultrasonography scanning during the 8 days before slaughtering. Experimental regression of
cysts was followed by rapid growth of follicles that reached the size of
cysts within 3-5 days. These young
cysts exhibited higher intrafollicular concentrations of
testosterone,
estradiol-17beta, and
progesterone than large early dominant follicles did in normal ovaries, but they exhibited similar concentrations of AMH. Later-stage
cysts were characterized by
hypertrophy of theca interna cells, high intrafollicular
progesterone concentration, and high
steroidogenic acute regulatory protein mRNA expression in granulosa cells.
Progesterone and AMH concentrations in the largest follicles (> or =10 mm) and
cysts were negatively correlated (r = -0.45, P < 0.01). Smaller follicles (<10 mm) exhibited higher intrafollicular
testosterone and
estradiol-17beta concentrations in ovaries with
cysts compared to normal ovaries. During follicular growth, AMH concentration dropped in follicles larger than 5 mm in diameter and in a similar way in ovaries with and without
cysts. In conclusion, enhanced growth and steroidogenesis in
antral follicles <10 mm preceded
cyst formation in cow ovaries. Intrafollicular AMH was not a marker of cystic development in the cow, but low AMH concentrations in
cysts were associated with luteinization.