Gonadotrophin and steroid concentrations in bovine follicular fluid and their relationship to follicle size.

The concentrations of LH, FSH and prolactin, and oestradiol-17 beta, androstenedione, testosterone and progesterone were measured in follicular fluid from small, medium and large bovine follicles. As follicle size increased, there was a significant increase in median fluid concentrations of prolactin (2-fold) and oestradiol-17 beta (14-fold) and a significant decrease in concentrations of LH (to 73%), androstenedione (to 30%) and testosterone (to 10%). There was no relationship between follicle size and fluid concentrations of FSH or progesterone, or between fluid concentrations of FSH and the relative concentrations of androgen and oestradiol-17 beta. As follicle size increased there was a significant increase in the proportion of follicles in which follicular fluid concentrations of oestradiol-17 beta exceeded those of androgen. There was a significant relationship between follicular fluid concentrations of prolactin and progesterone; as fluid prolactin concentrations increased, the maximum concentration of progesterone observed decreased.