Urinary oestrogen levels and follicle ultrasound measurements in clomiphene induced cycles with an endogenous luteinizing hormone surge.

Total oestrogen in urine and the ultrasonic size of the follicles were measured in relation to the onset of the endogenous luteinizing hormone (LH) surge (day 0) in 18 cycles induced with clomiphene citrate in an in-vitro fertilization programme. Oestrogen values in urine (microgram/24 h) increased progressively during the late follicular phase up to the day of the onset of the surge. The mean maximum follicle diameter (22.3, SD 4.7 mm) estimated by ultrasound was measured on day 0. At the onset of the LH surge, the values of urinary total oestrogen showed a better relation with the total volume of the first three follicles in order estimated by ultrasound (r = 0.71) than with the mean ultrasonic diameter of the leading follicle (r = 0.56). A wide range of individual values for both urinary oestrogen and follicle size was found. In another group of 32 women treated with clomiphene for recovery of oocytes used for research purposes, a good correlation was found between the mean ultrasonic follicle diameter 16 h before the laparoscopy and the follicle diameter calculated from the fluid volume at aspiration (r = 0.80). These results suggest that the decision when to give human chorionic gonadotrophin (hCG) in an in-vitro fertilization programme remains arbitrary in many individual cases. Apart from the oestrogen levels, the calculation of the size of all follicles, instead of only the leading one, may give further help in timing the hCG.