Changes in plasma levels of prolactin, in relation to those of FSH, oestradiol, androstenedione and progesterone around the preovulatory surge of LH in women

Elevated prolactin secretion during proestrus in mice: Absence of a defined surge

Throughout the reproductive cycle in rodents, prolactin levels are generally low. In some species, including rats, a prolactin surge occurs on proestrus with peak concentrations coinciding with the preovulatory luteinizing hormone (LH) surge. In mice, however, there are conflicting reports relating to the occurrence and timing of a proestrous prolactin surge. To gain further insight into the incidence and characteristics of this surge in mice, we have used serial tail tip blood sampling and trunk blood collection from both C57BL/6J (inbred) and Swiss Webster (outbred) mouse strains to build a profile of prolactin secretion during proestrus in individual mice. A clearly defined LH surge was detected in most animals, suggesting the blood sampling approach was suitable for detecting patterns of hormone secretion on proestrus. Despite this, levels of prolactin were quite variable between individuals. Overall both mouse strains showed a generalized rise in prolactin levels on the day of proestrus compared with levels seen in diestrus. This pattern is quite distinct from the discreet, circadian-entrained surge observed in rats.

Patterns of prolactin secretion

Prolactin is pleotropic in nature affecting multiple tissues throughout the body. As a consequence of the broad range of functions, regulation of anterior pituitary prolactin secretion is complex and atypical as compared to other pituitary hormones. Many studies have provided insight into the complex hypothalamic-pituitary networks controlling prolactin secretion patterns in different species using a range of techniques. Here, we review prolactin secretion in both males and females; and consider the different patterns of prolactin secretion across the reproductive cycle in representative female mammals with short versus long luteal phases and in seasonal breeders. Additionally, we highlight changes in the pattern of secretion during pregnancy and lactation, and discuss the wide range of adaptive functions that prolactin may have in these important physiological states.

Novel aspects of the endocrinology of the menstrual cycle

Ovarian control of gonadotrophin secretion is normally achieved via the feedback mechanisms mediated by oestradiol and progesterone. Evidence has been provided that nonsteroidal substances, such as inhibin A and B, participate in the negative feedback control of FSH secretion. Another nonsteroidal ovarian substance is gonadotrophin surge-attenuating factor (GnSAF), the activity of which is particularly evident in women undergoing ovulation induction. Accumulating evidence has suggested that GnSAF plays a physiological role during the menstrual cycle. In particular, this factor antagonizes the sensitizing effect of oestradiol on the pituitary response to gonadotrophin-releasing hormone during the follicular phase of the cycle. A hypothesis has been developed that, in the late follicular phase, the activity of GnSAF is reduced and this facilitates the sensitizing effect of oestradiol on the pituitary, thus enforcing the massive discharge of gonadotrophins at the midcycle LH surge. The interaction of oestradiol, progesterone and GnSAF on the hypothalamic-pituitary system provides a novel approach to explain the mechanisms which control LH secretion during the normal menstrual cycle. The ovarian control of gonadotrophin secretion during the normal menstrual cycle is achieved via negative and positive feedback mechanisms. The steroids oestradiol and progesterone are the main regulators; however, nonsteroidal substances, such as inhibin A and inhibn B, also participate. Accumulating evidence has demonstrated that another nonsteroidal ovarian substance, gonadotrophin surge-attenuating factor (GnSAF), plays a key role in the control of LH secretion during the follicular phase and at midcycle, providing thus a novel aspect in the ovarian control of gonadotrophin secretion during the human menstrual cycle. The ovarian control of gonadotrophin secretion during the normal menstrual cycle is achieved via negative and positive feedback mechanisms. The steroids oestradiol and progesterone are the main regulators; however, nonsteroidal substances, such as inhibin A and inhibn B, also participate. Accumulating evidence has demonstrated that another nonsteroidal ovarian substance, gonadotrophin surge-attenuating factor (GnSAF), plays a key role in the control of LH secretion during the follicular phase and at midcycle, providing thus a novel aspect in the ovarian control of gonadotrophin secretion during the human menstrual cycle.

Menopause and age-driven changes in blood level of fat- and water-soluble vitamins

OBJECTIVE

The purpose of this cross-sectional study was to assess the association of the menopausal transition with changes in vitamins.

METHODS

The study group comprised women aged 17-85 years from the Third National Health and Nutrition Examination Survey (NHANES), which was conducted between 1988 and 1994, and from the NHANES surveys conducted between 1999 and 2006. Menopausal status was defined using the time since the last period, < 2, 2-12, and > 12 months, for the pre-, peri-, and postmenopause, respectively. The data-cleaning technique employing serum follicle stimulating hormone activity resulted in pre-, peri- and postmenopausal samples encompassing the following age brackets: 17-50, 42-51, and 46-85 years. Statistical inferences were analyzed using non-parametric techniques.

RESULTS

Significant increases in vitamin A and vitamin E concentrations across all phases of the menopausal transition were observed. There was a gradual decrease in the vitamin C concentration across all stages of the menopause but a fairly stable concentration of vitamin B12. There was a statistically significant increase in vitamin D between the pre- and postmenopause. Body mass index correlated negatively with serum vitamin concentration in the pre- and postmenopause.

CONCLUSIONS

Vitamin A should be supplemented in postmenopausal women to decrease the risk of bone fracture. The daily diet should be supplemented with vitamin B12, to avoid possible neurological symptoms due to vitamin B12 deficiency, and with vitamin D to decrease the risk of developing secondary hyperparathyroidism. Due to an adverse influence on serum vitamin concentration, body mass index should be monitored in pre- and postmenopausal women.

Reproductive ageing in women

The traditional view in respect to female reproduction is that the number of oocytes at birth is fixed and continuously declines towards the point when no more oocytes are available after menopause. In this review we briefly discuss the embryonic development of female germ cells and ovarian follicles. The ontogeny of the hypothalamic-pituitary-gonadal axis is then discussed, with a focus on pubertal transition and normal ovulatory menstrual cycles during female adult life. Biochemical markers of menopausal transition are briefly examined. We also examine the effects of age on female fertility, the contribution of chromosomal abnormalities of the oocyte to the observed decline in female fertility with age and the possible biological basis for the occurrence of such abnormalities. Finally, we consider the effects of maternal age on obstetric complications and perinatal outcome. New data that have the potential to revolutionize our understanding of mammalian oogenesis and follicular formation, and of the female reproductive ageing process, are also briefly considered.

Ovarian feedback, mechanism of action and possible clinical implications

The secretion of gonadotrophins from the pituitary in women is under ovarian control via negative and positive feedback mechanisms. Steroidal and non-steroidal substances mediate the ovarian effects on the hypothalamic-pituitary system. During the follicular phase of the cycle, estradiol (E(2)) plays a key role, while circulating progesterone (at low concentrations) and inhibin B contribute to the control of LH and FSH secretion respectively. During the luteal phase, both E(2) and progesterone regulate secretion of the two gonadotrophins, while inhibin A plays a role in FSH secretion. The intercycle rise of FSH is related to changes in the levels of the steroidal and non-steroidal substances during the luteal-follicular transition. In terms of the positive feedback mechanism, E(2) is the main component sensitizing the pituitary to GnRH. Activity of a non-steroidal ovarian substance, named gonadotrophin surge-attenuating factor (GnSAF), has been detected after ovarian stimulation. It is hypothesized that GnSAF, by antagonizing the sensitizing effect of E(2) on the pituitary, regulates the amplitude of the endogenous LH surge at midcycle. Disturbances in the feedback mechanisms can occur in various abnormal conditions or after treatment with pharmaceutical compounds that interfere with the production or the action of endogenous hormones.

Temporal relations between plasma concentrations of luteinizing hormone, follicle-stimulating hormone, estradiol-17β, progesterone, prolactin, and α-melanocyte-stimulating hormone during the follicular, ovulatory, and early luteal phase in the bitch

Compared with other domestic animals, relatively little is known about the changes in, and temporal relations between, reproductive hormones around the time of ovulation in the domestic bitch. Therefore, plasma concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol-17beta, progesterone, prolactin (PRL), and alpha-melanocyte-stimulating hormone (alpha-MSH) were determined one to six times daily from the start of the follicular phase until 5 days after the estimated day of ovulation in six Beagle bitches. In all bitches, the pre-ovulatory LH surge was accompanied by a pre-ovulatory FSH surge. A pre-ovulatory PRL or alpha-MSH surge was not observed. The pre-ovulatory FSH and LH surges started concomitantly in four bitches, but in two bitches the FSH surge started 12 h earlier than the LH surge. The FSH surge (110+/-8 h) lasted significantly longer than the LH surge (36+/-5 h). In contrast with the pre-ovulatory FSH surge, the pre-ovulatory LH surge was bifurcated in four of six bitches. The mean plasma LH concentrations before (1.9+/-0.4 microg/L) and after (1.9+/-0.3 microg/L) the LH surge were similar, but the mean plasma FSH concentration before the FSH surge (1.6+/-0.3 U/L) was significantly lower than that after the FSH surge (3.1+/-0.2 U/L). In most bitches the highest plasma estradiol-17beta concentration coincided with or followed the start of the pre-ovulatory LH surge. In five of the six bitches the plasma progesterone concentration started to rise just before or concurrently with the start of the LH surge. In conclusion, the results of this study provide evidence for the differential regulation of the secretion of LH and FSH in the bitch. In addition, the interrelationship of the plasma profiles of estradiol-17beta and LH suggests a positive feedback effect of estradiol-17beta on LH surge release. The start of the pre-ovulatory LH surge is associated with an increase in the plasma progesterone concentration in this species.

The preovulatory serum estradiol pattern in natural IVF/ICSI cycles

PURPOSE

The aim of the study was to find whether inferences to the possible success of natural IVF/ICSI cycles could be drawn from the estradiol (E2) pattern.

METHODS

Sixty-eight women who underwent oocyte recovery in 98 natural cycles were recruited for the study. Daily serum E2 was measured in the preovulatory phase (-3 to +2 day). The E2 pattern was compared among four groups: Group A, unsuccessful egg retrieval; Group B, no fertilization; Group C, no implantation; and Group D, implantation.

RESULTS

There was no difference in mean E2 levels between groups. Only the ratio of E2 on day +1/E2 on day 0 was significantly lower in conception cycles in comparison with nonconception cycles. In cycles with a decreased E2 level on day +1, only the implantation rate was significantly higher in comparison with cycles with an increasing E2 level.

CONCLUSIONS

From the E2 pattern it is possible to make inferences about the likelihood of implantation but not the fertilization or oocyte recovery success.

Suppression of luteal phase, but not midcycle, prolactin levels by chronic follicular phase opiate antagonism

OBJECTIVE

To investigate whether establishment and maintenance of chronic opioid blockade throughout the follicular phase of the menstrual cycle influences midcycle and luteal phase prolactin levels.

DESIGN

Randomized, double-blind, crossover study.

SETTING

Academic research environment.

PATIENT(S)

Volunteers, aged 21-35 years, with regular menstrual cycles.

INTERVENTION(S)

Naltrexone (50 mg) or placebo were administered on cycle days 2-14. Blood samples were obtained in the early follicular phase and in the periovulatory and midluteal phases of the menstrual cycle.

MAIN OUTCOME MEASURE(S)

Serum prolactin levels.

RESULT(S)

In the early follicular phase, serum prolactin levels were equivalent in naltrexone (12.0 +/- 2.7 microgram/L; mean +/- SE) and placebo (12.1 +/- 2.9 micrograms/L) cycles. A statistically significant increase in serum prolactin was observed on the day of the LH surge (naltrexone: 22.6 +/- 3.7 micrograms/L; placebo: 21.7 +/- 2.7 micrograms/L; P < 0.05 versus early follicular phase), but no difference between treatments was observed. However, midluteal prolactin levels were statistically significantly lower in naltrexone cycles compared with placebo cycles (12.6 +/- 3.3 versus 15.4 +/- 3.0 micrograms/L; P < 0.05).

CONCLUSION(S)

Chronic blockade of opioid activities during the follicular phase does not affect midcycle prolactin increments, but withdrawal of opioid blockade may enhance opioid effects on prolactin levels in the luteal phase.

Effects of sex steroid hormones on the neuroendocrine system

Estrogen and progesterone are the most important ovarian steroid hormones regulating female fertility. They have a profound effect on the central nervous system. Target functions of sex steroids in the brain are: pituitary and hypothalamic hormone release, thermoregulatory and cardiocirculatory activities and behavior and mood changes. Furthermore, several studies have shown a correlation between brain neurotransmitters, neuropeptides and sex steroid hormones: they influence synthesis and release of norepinephrine, dopamine, serotonin, gonadotropin releasing hormone, beta-endorphin, corticotropin releasing factor and prolactin. Thus, oral hormone contraceptives inhibit the ovulatory process by blocking the activity of the hypothalamus-pituitary-gonadal axis. This inhibitory effect seems to be due to the action of both estrogens and progestins.

Synchronous secretion of LH and prolactin during the normal menstrual cycle

Integrated hourly concentrations of day-time prolactin and LH showed significant positive correlations (p < 0.05-0.001) on the day of the pre-ovulatory mid cycle LH surge (n = 3) and during the mid luteal phase (n = 6) in a group of regularly cyclic women. No correlations between these two hormones were seen during any other stage of the cycle. Consistent significant correlations were not evident between prolactin and oestradiol, prolactin and progesterone, LH and oestradiol or LH and progesterone during any other stage of the cycle.

Lactation, nutrition and fertility and the secretion of prolactin and gonadotrophins in Mopan Mayan women

The effect of lactation on menstrual cycles, ovulation and conception was studied in a group of non-contracepting Amerindian Mopan Mayan women. Anthropological observations of relevant events were made over a 21-month period. Blood samples were assayed to determine the plasma concentrations of prolactin, luteinising hormone, follicle stimulating hormone, human chorionic gonadotrophin, placental lactogen, oestrogen, progesterone and cortisol. The data show that: frequent and prolonged breast-feeding was associated with a marked increase in plasma prolactin concentrations to levels similar to those in lactating Gaing but higher than those in lactating Scottish women; ovulatory menstrual cycles and pregnancy occurred during frequent lactation; in lactating menstruating women there was an inverse correlation between fat weight and months post-partum. These data suggest that other factors as well as suckling account for the effects of lactation on fecundity.

Steroid control of central neuronal interactions and function

Steroids have potent actions on the brain which can be categorized as; (i) fast (approximately ms-s), (ii) intermediate (h-days), (iii) long-term reversible (days-weeks) and (iv) long-term irreversible. Here attention is focussed on the intermediate and long-term reversible effects of steroids with emphasis on glucocorticoids and oestrogen. Glucocorticoid negative feedback is generally classified as fast, delayed and long-term. Fast negative feedback would appear to depend mainly on a reduction in pituitary responsiveness to corticotrophin releasing factor-41 (CRF-41) and possibly arginine vasopressin (AVP). Delayed feedback is mediated by reduced AVP release into hypophysial portal blood and blockade of the ACTH response to CRF-41. Long-term negative feedback is a consequence of reduced CRF-41 and AVP release into portal blood. Lesion and electrical stimulation studies pinpoint the paraventricular nuclei as the main site at which glucocorticoids act to control ACTH release. Oestrogen at physiologically low plasma concentrations inhibits gonadotrophin secretion. At physiologically high plasma concentrations, such as those that occur during the preovulatory surge, oestradiol-17 beta stimulates the biosynthesis of LHRH mRNA and LHRH and the release of LHRH into hypophysial portal blood. Oestradiol also increases pituitary responsiveness to LHRH. The action of oestrogen on LHRH neurons is probably mediated by interneurons and may involve disinhibition; this view is supported by our in situ hybridization studies which show that oestrogen, in its positive feedback mode, significantly reduces the synthesis of proopiomelanocortin mRNA in arcuate neurons which when active are likely to inhibit LHRH neurons. The mechanism of action of oestrogen on the pituitary gland is not yet established, but clues from the action of the priming effect of LHRH suggests that oestrogen may potentiate phosphoinositide second messenger cascades. LHRH priming involves the synthesis of a 70 kDa protein the N-terminus of which is identical to an oestrogen-induced protein in the ventromedial hypothalamic nucleus involved in lordosis, and to that of phospholipase C alpha. Attention is drawn to the remarkable economy of the system by which a single steroid, oestrogen, has effects on the brain and pituitary gland which result in a co-ordinated sequence of amplifier cascades which lead first to the ovulatory surge of luteinizing hormone and then to mating behaviour, both of which are obviously essential for continuation of the species.(ABSTRACT TRUNCATED AT 400 WORDS)

Prolactin secretion in women during the oestradiol-induced luteinizing hormone surge with or without progesterone

To study the role of progesterone (P4) in the control of PRL increase during the midcycle LH surge, eight normally ovulating women were treated with i.m. injections of oestradiol benzoate (E2B) every 12 h during the early follicular phase of two different cycles (from cycle days 2 to 4). In the second cycle P4 injections were also given to the women every 12 h starting at the end of the E2B treatment (from cycle days 4 to 6). Circadian periodicity of serum PRL levels during the E2-induced LH surge did not differ significantly between the E2B and the E2B + P4 experiments. Evening PRL levels increased significantly in both experiments with a peak during the LH surge and no significant difference between them. We conclude that administration of P4 to normal women does not alter the increase in PRL secretion during the LH surge induced by exogenous oestrogen. It is suggested that P4 is not involved in the mechanism controlling midcycle PRL secretion.

Influence of preovulatory estradiol concentration on diurnal and pulsatile prolactin secretion patterns

We evaluated the effect of preovulatory concentrations of estradiol on the 24-hour profile of prolactin secretion in women with regular menstrual cycles. An estradiol preparation was chosen to allow comparison with physiologic events. Estradiol benzoate, 1 mg intramuscularly, was administered for 7 days to achieve estradiol concentrations just above preovulatory levels (424 +/- 54 pg/ml); 24-hour mean prolactin concentrations increased threefold (14.0 +/- 2.1 to 40.6 +/- 7.1 ng/ml). Prolactin pulse frequency increased significantly (p less than 0.001) during waking hours after estradiol benzoate administration. The diurnal pattern of prolactin secretion was maintained with estradiol benzoate, although the sleep acrophase often reached high concentrations (86 +/- 11 ng/ml). These results suggest in women with regular menstrual cycles: (1) that estrogen administration that achieves slightly greater than preovulatory estradiol concentrations can stimulate prolactin release, (2) that estradiol may elevate prolactin by increasing its pulsatile secretion, (3) that estradiol does not alter the diurnal pattern of prolactin secretion, (4) that estradiol concentrations just above preovulatory levels can be associated with markedly elevated prolactin concentrations.

Changes in serum prolactin levels during the follicular phase and the endogenous luteinizing hormone surge of cycles hyperstimulated with follicle stimulating hormone

The pattern of serum PRL levels during superovulation induction with pulsatile 'pure' FSH was investigated in 10 normally ovulating women. They were studied in two consecutive cycles, i.e. an untreated spontaneous and an FSH stimulated cycle. An endogenous LH surge occurred in all 10 spontaneous cycles and in five of the FSH cycles. Midcycle PRL levels were significantly higher in the FSH stimulated than in the spontaneous cycles (P less than 0.01). In both groups of cycles, circadian periodicity of serum PRL levels during the LH surge was different from that during the late follicular phase with higher levels at midnight, although in the FSH cycles PRL secretion showed a sustained increase over 24 h. A nadir of PRL levels was found between 0900 h and 1200 h. In contrast, progesterone secretion during the LH surge showed a nocturnal increase with the highest value between 0600 h and 1200 h and the lowest at midnight. In the FSH cycles without an LH surge, PRL levels increased as long as FSH administration was continued and showed a significant positive correlation with the increasing serum oestradiol levels (r = 0.77). We conclude that ovarian hyperstimulation is a potent stimulus of PRL secretion in women. It is suggested that the midcycle endogenous LH surge facilitates the evening PRL secretion, while induction of multiple folliculogenesis amplifies the 24 h pattern of PRL secretion.

Superovulation with exogenous gonadotropins does not inhibit the luteinizing hormone surge

The administration of human chorionic gonadotropin to women undergoing superovulation with exogenous gonadotropins was delayed in order to document the occurrence of a surge of luteinizing hormone (LH). An LH surge was seen to occur in 10 of 10 women receiving clomiphene citrate (CC) and pulsatile human menopausal gonadotropin (hMG); in 10 of 12 women treated with pulsatile hMG alone; and in 12 of 14 women treated with single daily injections of hMG without CC. The height of the surge was attenuated in all cycles and the timing of its onset was significantly earlier among women receiving single daily injections of hMG. Possible mechanisms for these findings are discussed.

Modulating actions of estradiol on gonadotropin-releasing hormone-stimulated prolactin secretion in postmenopausal individuals

The temporal aspects of estrogen treatment on serum prolactin concentrations basally and in response to a 10 micrograms intravenous injection of gonadotropin-releasing hormone were assessed in eight postmenopausal women. The response of prolactin to gonadotropin-releasing hormone stimulation was compared with that of follicle-stimulating hormone and luteinizing hormone obtained simultaneously. Basal serum prolactin increased significantly (p less than 0.001) in response to estrogen treatment, and a positive correlation was found between the serum concentrations of estradiol and prolactin (r2 = 0.266; p = 0.0011). Gonadotropin-releasing hormone induced a significant increase in serum prolactin concentrations, which was greater after 5 to 10 days of estrogen treatment compared with that in the estrogen-depleted state (p = 0.031). No correlation was found between gonadotropin-releasing hormone-stimulated prolactin and luteinizing hormone or follicle-stimulating hormone release. These data demonstrate that estrogen treatment of previously hypoestrogenemic postmenopausal women potentiates gonadotropin-releasing hormone-stimulated prolactin release. Furthermore, our data suggest that the previously described paracrine interaction between the gonadotropins and lactotropes exerted by gonadotropin-releasing hormone does not appear to be mediated via increased gonadotropin release.

The temporal relationship between melatonin and prolactin in women

The relationship between the concentrations of melatonin and prolactin (PRL) over 24 hours has been investigated. Two peaks in PRL concentrations were distinguished: an evening peak (at 8:00 P.M.) and a nocturnal peak (at 6:00 A.M.). Melatonin concentrations showed a single peak (at 2:00 A.M.). In both the follicular and luteal phases of the menstrual cycle, melatonin increased 2 to 3 hours after the evening increase in PRL and 4 hours before the nocturnal rise in PRL concentrations. Oral administration of melatonin stimulated PRL release. The PRL response varied with menstrual cycle stage being significantly greater in the ovulatory (P less than 0.001) and luteal (P less than 0.01) phases than in the follicular phase. The results suggest that melatonin may be involved in control of the nocturnal PRL increase.

Luteal phase after ovarian hyperstimulation

The luteal phase was investigated in 17 women with normal menstrual cycles and tubal infertility who were superovulated with clomiphene (9 cycles), clomiphene plus pulsatile human menopausal gonadotrophin (hMG) (12 cycles) and clomiphene plus pulsatile follicle stimulating hormone (FSH) (11 cycles) during an in-vitro fertilization programme. Follicles were aspirated 34-36 h after the onset of the endogenous LH surge. Urinary total oestrogen levels during the first 6 days of the luteal phase were significantly higher, the duration of the luteal phase was significantly shorter and the luteal levels of urinary pregnanediol were significantly lower in the two combination treatment cycles than in the clomiphene only cycles. When the three treatment groups were combined the mid-luteal peak pregnanediol levels and the duration of the luteal phase showed significant negative correlations with plasma or urinary oestrogen levels during the follicular and the luteal phase. It is suggested that the luteal function in cycles superovulated with clomiphene/hMG or clomiphene/FSH is disrupted and this is related to the high amounts of circulating oestrogen.

Relationships between the characteristics of endogenous luteinizing hormone surge and the degree of ovarian hyperstimulation during superovulation induction in women

Ovarian hyperstimulation was induced in 17 normally cycling women undergoing in-vitro fertilization (IVF) and embryo transfer with clomiphene (9 cycles), clomiphene followed by pulsatile hMG (12 cycles) or clomiphene followed by pulsatile FSH (11 cycles). Hyperstimulation was greater with the combined treatments than with clomiphene alone. In all 32 cycles an endogenous LH surge occurred. The peak values and the duration of the LH surge showed significant negative correlations with the plasma oestradiol levels, the number of the follicles and the total follicular fluid volume aspirated at laparoscopy. We suggest that during superovulation induction for IVF, the endogenous LH surge is attenuated by factors which are related to the degree of ovarian hyperstimulation.

Endogenous luteinizing hormone surge in women during induction of multiple follicular development with pulsatile follicle stimulating hormone

In this study nine consecutive normally cycling women undergoing in-vitro fertilization (IVF) were superovulated with clomiphene citrate followed by pulsatile 'pure' FSH injected s.c. via a pump (28 IU every 3 h). All women displayed an endogenous LH surge, which was markedly attenuated in most of the cases (peak value 44.5 +/- 5.9 U/l, duration 29.2 +/- 1.2 h, mean +/- SEM) as compared to spontaneous cycles. An increase in serum progesterone levels before the onset of the LH surge was seen in only one woman at a time when the LH values were low. During the LH surge serum progesterone levels increased significantly in all patients (12.7 +/- 1.90 nmol/l vs 4.74 +/- 1.57 nmol/l at the onset of the surge, mean +/- SEM, P less than 0.05) indicating follicular luteinization. Very high oestradiol levels in serum were found at the onset of the LH surge (7504 +/- 898 pmol/l, mean +/- SEM). Preovulatory oocytes were recovered from all women through a laparoscope 34-36 h after the beginning of the LH surge and embryos were replaced to them after IVF. One ongoing clinical pregnancy occurred. In contrast to results in monkeys, these results demonstrate for the first time that normally cycling women superovulated with clomiphene pulsatile 'pure' FSH will display an endogenous LH surge. Although the surge is attenuated implantation can occur.

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.

Pulsatile release of LH and oestradiol during the periovulatory period in women

Blood was collected every 8 h in five women from Day 10 of the menstrual cycle for 5-7 d for the measurement of LH, oestradiol and progesterone. In all women the LH surge started between 2400 and 0800 h before there was any significant decline in the concentration of oestradiol. In order to investigate the pulsatile secretion of LH and estradiol during the mid-cycle surge, blood samples were collected every 5 min for up to 5 h. Immediately before and during the LH surge there were numerous episodic pulses of LH with an interpulse interval (44 +/- 7 min) very similar to that observed in two women with hypergonadotrophic hypogonadism (48 min). The concentration of oestradiol fluctuated in a similar manner although it was not always possible to relate each pulse of oestradiol to a corresponding pulse of LH. The mid-cycle surge of LH is characterized by frequent pulses of high amplitude. These results are compatible with the view that the positive feedback effect of oestradiol is due not only to enhanced sensitivity of the anterior pituitary to LHRH but also to the high frequency of LHRH pulses released from the hypothalamus.