Carolyn Pheteplace. Department of Obstetrics and Gynecology,

Transcription

1 Department of Obstetrics and Gynecology, Harvard Medical School, and Department of Surgery, Peter Bent Brigham Hospital. Boston, Massachusetts, U. S. A. FOLLICLESTIMULATING HORMONE AND LUTEINIZING HORMONE IN SERUM DURING THE MENSTRUAL CYCLE DETERMINED BY RADIOIMMUNOASSAY By Melvin L. Taymor, Toshihiro Aono and Carolyn Pheteplace with the assistance of Gary Page ABSTRACT The serum levels of FSH and LH were determined in 11 normal menstrual cycles by radioimmunoassay. The results of LH assay demonstrated a consistent pattern with a sharp 3 to 4 fold increase occurring on the average 13.9 days before the next menses. The changes in FSH levels during the cycle were neither as marked nor as consistent. Three distinct patterns seemed to emerge. However, the mean levels of FSH from the 11 cycles demonstrated a significant high level 12 days before, a low level 1 day before and another rise 1 day after the midcycle peak of LH. The levels of luteinizing hormone (LH) excretion in the urine during the nor mal menstrual cycle have been well documented by bioassay techniques. Re ports concerning folliclestimulating hormone (FSH) excretion during the cycle have been conflicting (McArthur et al. 1958; Taymor 1961; Fukushima et al. 1964; Becker 8c Albert 1965; Rosemberg 8c Keller 1965). This has undoubtedlybeen because the bioassay methods available are not sufficiently sensitive to allow for the simultaneous measurement of both FSH and LH in a single * Postdoctoral Fellow of the Population Council, New York. Present address: Depart ment of Obstetrics and Gynecology, Osaka University, Medical School, Osaka, Japan. Supported in part by Grant No. FR of the USPHS and a Grantinaid from HoffmannLaRoche, Inc., Nutley, New Jersey.

2 24 hour urine specimen. Pooling of the urine adequate for statistical needs can often result in a loss of the details of cyclic hormone change. Recently the radioimmunoassay method has been introduced to measure both FSH (Midgely 1967; Faiman 8c Ryan 1967; Aono 8c Taymor 1968) and LH (Bagshawe et al. 1966; Midgely 8c Jaffee 1966; Odell et al. 1967; Aono et al. 1967). The methods are sufficiently sensitive to allow for the simultaneous measurement of both FSH and LH in unconcentrated serum. This report describes the serum FSH and LH levels in 11 normal menstrual cycles from 9 subjects determined by radioimmunoassay. MATERIALS AND METHODS Collection of specimens The 9 subjects were nurses and laboratory personnel who had no history of menstrual disorders. Their age ranged from 20 to 28 years and none were parous. The cycle length varied from 25 to 35 days with the mean of 29.3 days. In the initial 5 cycles, the venous blood was drawn at daily intervals through the first 20 days of the menstrual cycle and every other or every third day until menses occurred. In this group, the specimen was obtained at various times between 9 a. m. and 5 p. m. In the latter 6 cycles, daily blood was collected throughout the cycle and an attempt was made to draw the blood at approximately the same time from any one individual. Blood was allowed to clot at 4 C overnight and serum was separated by centrifugation. The aliquots of serum were stored at 15 C until subsequently analyzed. Each subject kept a record of her basal body temperature (BBT) and re ceived no medication during the test cycle. Performance of the radioimmunoassay The procedures for the radioimmunoassay for FSH and LH have been previously described in detail (Aono et al. 1967; Aono Se Taymor 1968). The sensitivities of the assays were 4mIU/ml for FSH and 2mIU/ml for LH. A standard dose response curve was run with each assay. FSHLER6774* was employed as the standard material for FSH assay, and LHDEAEI2** for LH assay. Both hormones were purified pituitary gonadotrophin preparations and had a potency of 16.2 IU/mg*** and 1660 IU/mg*** respectively. The sera of postmenopausal women, containing high FSH or LH activity, were tested at different dilutions, and it was found that the dose response curve was parallel to the standard curve for purified FSH or LH. The assay was performed in undiluted serum in duplicate utilizing 0.4 ml for the FSH assay and 0.2 ml for the LH assay. The mean value of the duplicate determina tions was used to express the results. * Human pituitary FSH, generously supplied by the National Pituitary Agency, Baltimore, Maryland. ** Human pituitary LH, generously supplied by Dr. Anne Hartree, Cambridge, England. *** International Units in terms of the Second International Reference Preparations of Human Menopausal Gonadotrophin (2nd IRPHMG).

3 The precision of present assays expressed as the standard deviation was calculated according to Snedecor (1956). The standard deviation (s) is given by the formula: $ ( dv2nyi* = where d is the difference between results in a duplicate determination and is the number of duplicate determinations performed. The precision of the assay systems are shown in Table 1. It is noted that the standard deviation of FSH in the range of 10.0 to 19.9 miu/ml is similar to that of LH in the same range. RESULTS Individual cycles The pattern of serum levels of LH in each of the 11 menstrual cycles was quite consistent. In all cases, a fairly low constant LH level was noted in the follicular phase. At midcycle there was a sharp rise in the LH level that took between 1 and 2 days to reach its maximum. The peak levels were 2 to 8 times the basal levels. The LH level then fell off sharply, and the luteal phase levels were similar to the follicular phase levels. The interval between the LH peak and onset of the next menses was quite constant from cycle to cycle. The LH peak preceded the next menses by 13 to 16 days in all cases, with a mean of 13.9 days. In 5 instances the peak of LH levels coincided with the low point of BBT. The LH peak occurred 3 days before the low point of BBT in 2 cycles, one day before in 3 cycles and 1 day after in 1 cycle. The changes in the FSH levels were relatively small and in addition were not as consistent as the changes in LH. Three general patterns were noted. In the first (Fig. 1) the FSH levels were high early in the follicular phase and gradually fell off to a low point just before the midcycle LH surge. There was then a secondary rise in the FSH level just before, during or Estimate of precision expressed Range (miu/ml) Table 1. as the standard deviation of results from their means. Standard deviations 1.11 FSH (54)* 1.17 (145) 1.74 (75) t T t 1.75 (136) 1.97 (132) * Number of duplicate determinations in parenthesis. t Number of determinations was too small to derive standard deviation.

4 CG. April 1967 LH miu/ml. FSH miu/ml BBT 97.5 DAY OF CYCLE Fig. 1. Serum levels of FSH and LH during a normal menstrual cycle. slightly after the peak of LH. The FSH levels then fell once again during the luteal phase. Six out of the 11 cycles were classified in this pattern. A second pattern (Fig. 2) showed follicular and midcycle peaks of FSH similar to those in the preceding pattern, but in addition there were slowly rising levels of FSH late in the luteal phase. Three cycles demonstrated this pattern. The third pattern (Fig. 3) showed very little change throughout the men strual cycle except a small peak of FSH found around the midcycle. Two cycles, both from the same subject, demonstrated this pattern. Composite cycle An attempt to composite the individual cycles was made according to the day of LH peak. The day of LH peak was identified as day 0 and days pre ceding this day were assigned to 1, 2, etc. and the day after the LH peak became +1, +2, etc. The mean value of FSH and LH with the standard error of the mean are

5 J.D. April 1967 LH mlu / ml. FSH mlu / ml. BBT 98.5 DAY OF CYCLE Fig. 2. Serum levels of FSH and LH during a normal menstrual cycle. charted together with the mean BBT levels in Fig. 4. The mean levels and fiducial limits (P = 0.05) are listed in Table 2. The mean LH level in follicular and luteal phase fluctuated between 4.3 and 7.5 miu/ml. The peak level of LH was 29.3 miu/ml, and there was no overlapping of fiducial limits of the mean with another day of the cycle. The low point of composite BBT was found on day 0. The mean FSH curve showed the highest level to be on the 12th day before the LH peak with a mean level of 22.7 miu/ml. The lowest level, 14.9 miu/ml occurred on day LA second peak of FSH occurred on day +1 with a mean level of 20.8 miu/ml, and FSH levels fluctuated throughout the remainder of the cycle. There was no overlap of fiducial limits in mean FSH levels between the lowest point and the two peaks. The relatively wide range of standard error and fiducial limits in both FSH and LH levels found at the end of the cycle was partially due to the small number of samples obtained at the end of the cycles.

6 P. R. July 1967 oo. LH FSH LH miu/ml. FSH nlu/ml. DAY OF CYCLE Fig. 3. Serum levels of FSH and LH during a normal menstrual cycle. DISCUSSION The cyclic changes in serum levels of LH observed in this study by radio immunoassay were similar to the urinary excretion changes previously observed by bioassay (McArthur et al. 1958; Taymor 1961; Fukushima et al. 1964; Becker 8c Albert 1965; Rosemberg 8c Keller 1965). However, the surge seen in this present study appeared to be of shorter duration. Studies performed at 6 and 12 h intervals may reveal that the LH peak is even still briefer in duration. The cyclic changes in FSH levels were neither as dramatic nor as con sistent. No uniform pattern was observed. However, the appearance of more than one pattern in individual cycles has been described in urinary excretion studies by bioassay (Taymor 1967; Rocca 8c Albert 1967), and these have been similar to the patterns observed in this study by radioimmunoassay. Further more, the mean pattern demonstrated significant cyclic changes. There was in variably a low level of FSH excretion just prior to the midcycle surge of LH. This was significantly different from the highest follicular phase level and from the subsequent second rise in FSH level. That this second rise of FSH was not due to the lack of specificity of the assay, nor to cross reaction between FSH and LH, was confirmed by the fact that in individual cycles the secondary rise of FSH coincided exactly with the midcycle surge of LH in only 1 cycle.

7 SERUM FSH mlu / ml. DEVIATION FROM LH PEAK IN DAYS Fig. 4. Mean serum levels of FSH and LH during 11 Peak of LH in each cycle is the point of reference. normal menstrual cycles. Moreover our previous report (Aono 8c Taymor 1968) showed that the FSH assay results were not affected by LH unless the ratio of LH to FSH in terms of IU became more than 20. The wide fiducial limits in the majority of the mean levels of FSH were undoubtedly augmented by the fact that the variations in FSH in individual cycles occurred on different days relative to the arbitrarily selected point of midcycle peak of LH. Despite this some significant changes remained evident. This general pattern observed here was consistent with the mean excretion levels of FSH described by Stevens (1967) by bioassay, and more recently by Faiman 8c Ryan (1967), utilizing radioimmunoassay. The relatively small changes in FSH and LH excretion during the follicular phase suggest that the human follicle requires only this constant low level of stimulation to bring about beginning maturation. Meyer 8c Bradbury (1960) demonstrated that the presence of oestrogen in ovarian tissue augments the effect of gonadotrophins on follicle growth. It is conceivable, then, that once oestrogen production is stimulated, follicular development can continue without

8 Table 2. Mean serum levels of FSH and LH during 11 menstrual cycles. Days from LH peak Mean LH miu/ml Fiducial limits = (P 0.05) Mean FSH miu/ml Fiducial limits = (P 0.05) I S IS increasing levels of FSH and LH. The declining levels of FSH prior to the midcycle surge is undoubtedly the result of the inhibitory action of rising oestrogen levels on the hypothalamicpituitary pathway. Information derived from this line of investigation can place both the therapeutic induction of ovulation and the inhibition of ovulation on a firmer physiologic basis. Unanswered as yet is the exact time relationship of the midcycle surge of LH

9 to ovulation, as well as the significance of the second rise in FSH. Studies which more definitively pinpoint ovulation, such as corpus luteum biopsies, may provide additional answers to our developing knowledge of hypophysealovarian relationships. REFERENCES Aono T., Goldstein D. P., Taymor M. L. & Dolch K.: Amer. J. Obstet. Gynec. 98 (1967) 996. Aono T. Se Taymor M. L.: Amer. J. Obstet. Gynec. 100 (1968) 110. Bagshawe K. D., Wilde C. E. 8 Orr A. H.: Lancet 1 (1966) 118. Becker K. L. 8 Albert.: J. clin. Endocr. 25 (1965) 962. Faiman C. L. Se Ryan R. J.: J. clin. Endocr. 27 (1967) Fukushima M., Stevens V. C. Gaunt C. L. Se Vorys N.: J. clin. Endocr. 24 (1964) 205. McArthur J. W., Worcester J. 8c Ingersoll F. M.: J. clin. Endocr. 18 (1958) Meyer J. E. Sc Bradbury J. T.: Endocrinology 66 (1960) 121. Midgely A. R. Jr.: J. clin. Endocr. 27 (1967) 295. Midgely A. R. Jr. Se Jaffe R. B.: J. clin. Endocr. 26 (1966) Odell W. D., Ross G. T. Se Rayford P. L.: J. clin. Invest. 46 (1967) 248. Rocca D. Se Albert.: Proc. Mayo Clin. 42 (1967) 536. Rosemberg E. 8c Keller P. J.: J. clin. Endocr. 25 (1965) Snedecor G. W.: Statistical Methods, 5th ed. Iowa State College Press, Ames, Iowa (1956). Stevens V. C. In: Recent Research on Gonadotrophic Hormones, Bell. T. and Loraine J.., eds., E. & S. Livingstone, Edinburgh (1967) 227. Taymor M. L.: J. clin. Endocr. 21 (1961) 976. Taymor M. L. In: Recent Research on Gonadotrophic Hormones, Beli E. T. and Loraine J.., eds., E. & S. Livingstone, Edinburgh (1967) 230. Received on April 29th, 1968.