The following steroids were estimated in five samples of normal bovine follicular fluid, and in twenty-four samples of cyst fluid from cows with cystic ovaries: progesterone, 17α-hydroxyprogesterone, androstenedione, oestrone and oestradiol-17β. 20β-Hydroxypregn-4-en-3-one was also found in two samples of cyst fluid. No testosterone could be detected in any of the samples assayed.
Oestradiol-17β was the major steroid present in all five samples of follicular fluid. The concentration of oestradiol-17β was significantly lower (P<0·01) in the cyst fluid.
Many of the cyst fluid samples contained large amounts of progesterone, but little or no detectable 17α-hydroxyprogesterone, androstenedione, oestrone or oestradiol-17β. Histological examination of the cyst wall in a number of these cases showed atretic or luteinization changes. In one case where luteinization had occurred, 20β-hydroxypregn-4-en-3-one was also present in the cyst fluid.
There was no obvious correlation between the behavioural characteristics of the 'cystic cows' and the nature or amount of the steroids present in the cyst fluid. Thus the steroid concentrations in nine 'cystic cows' with normal oestrous cycles did not differ significantly (P>0·05) from the concentrations in seven nymphomaniac cows.
The absolute concentrations and relative amounts of the various steroids differed greatly, both between animals and within the same animal. It is therefore concluded that the cyst itself is not the primary defect in cystic ovarian disease. Both histologically and endocrinologically the cyst appears to be a degenerative structure. In the normal follicle, follicular growth and endocrine activity seem to accompany one another; in the cyst, on the other hand, follicular growth continues whilst endocrine activity is waning.