Influence of menstrual cycle on QT interval dynamics

OBJECTIVES: The aim of this study was to investigate the effects of the menstrual cycle on QT interval dynamics and the autonomic tone in healthy women. METHODS: Holter ECGs were recorded in 11 healthy women aged 18-32 years during the follicular and luteal phases of their regular menstrual cycle. The interval from QRS onset to the apex (QaT) and to the end of the T-wave (QeT), the interval between the apex and the end of the T-wave (Ta-e), and RR intervals were measured automatically in the course of 24 hours by Holter ECGs. The QeT/RR, QaT/RR, and Ta-e/RR relationships were evaluated in each subject. The autonomic tone was assessed by the serum catecholamine level at rest and heart rate variability was measured by Holter ECGs. RESULTS: (1) The follicular and luteal phases did not differ significantly with respect to the slopes of the QeT/RR, QaT/RR, and Ta-e/RR relationships. However, QeT and QaT intervals were significantly shorter for all RR intervals in the luteal than in the follicular phase (P < 0.0001). (2) The serum progesterone concentration was significantly higher in the luteal than in the follicular phase (P < 0.001). (3) Noradrenaline was significantly higher in the luteal than in the follicular phase (P < 0.05). There was no significant difference in the follicular and luteal phases with respect to heart rate variability measurements. CONCLUSIONS: Our results suggest that the menstrual cycle affects the QT intervals. The observed shorter QT interval during the luteal than the follicular phase may be attributable to the increase in serum progesterone and sympathetic tone.     

健康女性月经周期乳腺超声影像改变与雌孕激素水平的相关性分析

目的：分析健康妇女月经不同时期乳腺超声影像特点,进而探讨其与血清雌、孕激素水平的关系,以期为行性激素补充治疗（HRT ）妇女的乳腺检测提供参考。方法自2012年3月至2013年3月在攀枝花市妇幼保健院征集正常月经且无乳腺疾病的健康女性98例,确定其黄体期与晚卵泡期,通过乳腺超声检测,观察月经不同时期乳腺体层厚度和导管宽度及与雌、孕激素水平的关系,乳腺腺体声像图改变与雌二醇与孕酮的关系,乳房胀疼与乳腺结构改变以及雌、孕激素水平的关系。结果在月经不同时期,乳腺体层厚度与导管宽度有周期性变化,与黄体期比较,晚卵泡期的乳腺体层厚度与雌二醇水平均减少,而导管宽度则增加,但两者比较差异无统计学意义（P＞0．05）;孕酮值则降低明显,差异有统计学意义（ P＜0．01）。在98例健康女性之中,乳腺腺体结构改变者有43例（43．88％）,与乳腺结构改变者比较,乳腺结构未改变者黄体期的雌二醇、孕酮值均明显降低,雌二醇/孕酮则明显升高,差异具有统计学意义（P＜0．05）,晚卵泡期的雌二醇、雌二醇/孕酮明显降低,孕酮值则明显升高,差异有统计学意义（ P＜0．05）。超声检查中20例乳腺增生样改变者均存在明显的乳房胀疼,26例无乳房胀疼者中有8例（30．77％）存在乳腺结构改变,差异有统计学意义（ P＜0．01）。与乳房胀疼者比较,未有乳房胀疼者黄体期的雌二醇、孕酮值均明显降低,雌二醇/孕酮则明显升高,差异有统计学意义（P＜0．05）,晚卵泡期的雌二醇、雌二醇/孕酮明显降低,孕酮值则明显升高,差异有统计学意义（P＜0．05）。结论随着月经周期的变化,乳腺腺体声像图表现亦随之变化,乳房胀疼与乳腺腺体结构改变相关;而乳腺腺体结构改变和乳房胀疼与黄体期雌、孕激素水     

Erythrocyte cation fluxes during the menstrual cycle in normal female subjects

1. Studies of erythrocyte cation transport mechanisms in vitro were performed on eight normotensive, premenopausal female subjects at the mid-points of the follicular and luteal phases of their menstrual cycles. Concurrent plasma concentrations of 17 beta-oestradiol, progesterone, aldosterone and renin activity were measured. 2. Ouabain-resistant, frusemide-resistant rubidium influx (an index of passive potassium diffusion) was significantly lower in the luteal than the follicular phase. 3. In further studies in four of the eight subjects, the mean rate constant of the rubidium influx measurement was also lower in the luteal than in the follicular phase. 4. There were no changes in Na+-K+ co-transport, sodium pump activity or intracellular cation concentrations throughout the cycle. 5. There was a tenfold fall in the mean plasma 17 beta-oestradiol/progesterone ratio, as well as increases in plasma aldosterone concentration and renin activity between the mid-follicular and mid-luteal phases. 6. We conclude that changes in plasma oestrogen/progesterone ratio during the menstrual cycle may be associated with alterations in passive potassium diffusion.     

Changes in central arterial pressure waveforms during the normal menstrual cycle.

BACKGROUND: Changes in estradiol and progesterone during the human menstrual cycle may impact vascular and cardiac function. Renin-angiotensin-aldosterone system (RAAS) hormones increase during the luteal phase of the menstrual cycle and may antagonize the vascular effects of estradiol. This study was designed to investigate central arterial changes, cardiac function, and RAAS activity in response to gonadal steroid variations during the menstrual cycle. METHODS: We studied 15 women during the follicular and midluteal phases with determination of estradiol, progesterone, hormones of the RAAS, and spot urine sodium and creatinine levels. Central pulsatile hemodynamics was evaluated using calibrated carotid tonometry and central aortic Doppler flow. Systolic ejection period (SEP) and systolic pressure time integral (SPTI) were computed from carotid pressure waveforms. RESULTS: Levels of estradiol, progesterone, and RAAS hormones were higher in the luteal phase. SEP and SPTI were lower during the luteal phase, whereas central and peripheral blood pressures and measures of arterial stiffness were unchanged between the two phases. The urine sodium-to-creatinine ratio was similar at both phases. CONCLUSION: Central arterial stiffness does not differ between the follicular and midluteal phases of the menstrual cycle in healthy women, despite significant changes in estradiol and progesterone levels. Systole was shortened during the midluteal phase. RAAS activation during the luteal phase may be responsible for a lack of the expected estradiol-mediated reduction in arterial stiffness between the two phases of the menstrual cycle. Because load was unchanged, the decrease in SEP and SPTI may represent a direct effect of estrogen, progesterone, or RAAS activation on ventricular function.     

Haemodynamic responses to psychosocial stress during the menstrual cycle.

1. The haemodynamic effects of hormonal changes during the menstrual cycle were examined in 11 normotensive women (age 20-46 years). The subjects were studied on days 2-8 (follicular phase) and days 18-26 (luteal phase) in a randomized order. A standardized mental stress test and a 24 h recording of ambulatory blood pressure and heart rate were performed. 2. Pre-stress resting levels of heart rate and blood pressure were similar during the two phases of the menstrual cycle. 3. During mental stress, the heart rate response was significantly greater during the luteal phase than during the follicular phase (14.7 versus 9.7 beats/min; P less than 0.05). 4. Blood pressure, plasma catecholamine concentrations and subjective stress experience increased significantly in response to stress, without any significant differences between the two phases. 5. During 24 h ambulatory monitoring, higher levels of systolic blood pressure and heart rate were observed in the luteal phase than in the follicular phase (P less than 0.005 and P less than 0.0001, respectively). 6. These data indicate that cyclic variations in female sex hormones not only affect systolic blood pressure and heart rate, but also alter the haemodynamic responses to psychosocial stress.     

Homocysteine during the menstrual cycle in depressive women

BACKGROUND: Two possible factors that may have a causal relation with both depressive disorder and cardiovascular disease are elevated homocysteine and steroid hormones. Our previous study found significant changes in the plasma homocysteine concentration during the menstrual cycle in healthy women. The purpose of this study therefore was to test homocysteine in depressive women treated with fluoxetine during the menstrual cycle. MATERIALS AND METHODS: Thirteen premenopausal women suffering from mixed anxiety-depressive disorder and a control group of 15 healthy women were enrolled in this study. The homocysteine concentration was determined by high-performance liquid chromatography with fluorescence detection, and estradiol, progesterone and cortisol by RIA methods. RESULTS: We found significantly higher plasma homocysteine concentrations in the follicular phase than in the luteal phase of the menstrual cycle in both the depressive group (P < 0.003) and the controls (P < 0.0009). Moreover, the patient values of total homocysteine were significantly higher in the follicular phase (P < 0.03) and also in the luteal phase (P < 0.007) than the values of the controls. Estradiol and cortisol were significantly higher in the follicular phase of the patients compared with the control group. CONCLUSION: According to our results, women suffering from mixed anxiety-depressive disorder have not only significantly different concentrations of homocysteine in the follicular and luteal phase of the menstrual cycle but also higher plasma homocysteine compared with healthy women. More elevated homocysteine in the depressive than in the healthy premenopausal women points to the notion that psychological factors might be important when considering the homocysteine concentration.     

Sexual function and endocrine profile in fertile women with type 1 diabetes

OBJECTIVE: Aims of this study were 1) to assess sexual function and endocrine profile among fertile type 1 diabetic women during the follicular and luteal phases of the menstrual cycle, 2) to compare these results with those obtained among healthy fertile women who served as control subjects, and 3) to explore the correlations between sexual function and endocrine milieu among patients and control subjects during the follicular and luteal phases of the menstrual cycle. RESEARCH DESIGN AND METHODS: Fifty fertile women with type 1 diabetes and 47 healthy control subjects completed a semistructured medical interview and filled in self-administered validated instruments to evaluate sexual function, depression, and sexual distress. Venous blood samples were drawn to measure glycated hemoglobin and an endocrine profile during either the follicular or the luteal phase of the menstrual cycle. RESULTS: Type 1 diabetic women had decreased sexual function and increased sexual distress compared with control subjects during the luteal, but not the follicular, phase of the menstrual cycle. During the follicular phase, patients had lower estrogenic basal tone, lower "weak" androgen (namely Delta4-androstenedione and dehydroepiandrosterone sulfate) production, and lower free-triiodothyronine and free-thyroxine levels compared with control subjects. During the luteal phase, total testosterone levels were higher in patients than control subjects, while 17beta-estradiol and progesterone levels were lower in patients than control subjects. CONCLUSIONS: Among type 1 diabetic women, sexual function and sexual distress vary according to the phase of the menstrual cycle. This finding may have implications on the clinical assessment of sexual function in type 1 diabetic women.     

Effects of cocaine on luteinizing hormone in women during the follicular and luteal phases of the menstrual cycle and in men

Cocaine stimulates luteinizing hormone (LH) release in rhesus monkeys and in men, but its effects on LH in women are unknown. Cocaine (0.2 and 0.4 mg/kg i.v.) was administered to groups of follicular and luteal phase women (N = 22) and to men (N = 12) to examine the influence of gender and menstrual cycle phase on cocaine and LH interactions. All subjects met American Psychiatric Association Diagnostic and Statistical Manual IV criteria for cocaine abuse, and menstrual cycle phase was verified by estradiol and progesterone measures. Baseline LH levels were equivalent between groups. Peak cocaine levels did not differ significantly between men and women and averaged between 87 +/- 21 and 124 +/- 18 ng/ml after 0.2 mg/kg cocaine and between 227 +/- 22 and 287 +/- 21 ng/ml after 0.4 mg/kg cocaine. The lower dose of cocaine (0.2 mg/kg) significantly increased LH levels in men (P < 0.001) but not in women at either phase of the menstrual cycle. The higher dose of cocaine (0.4 mg/kg) stimulated significant increases in LH in men (P < 0.001) and in women at both phases of the menstrual cycle (P < 0.004-0.001). Although cocaine's effects on LH in women were dose-dependent, there were no significant differences as a function of menstrual cycle phase. LH remained significantly elevated longer in men (32 min) than in women (8 and 12 min). This gender difference in cocaine's potency in stimulating LH was unexpected.     

Sensitivity to cold pressor pain in dysmenorrheic and non-dysmenorrheic women as a function of menstrual cycle phase

Pain responses (threshold, tolerance, and visual analog ratings) to the cold pressor task were studied in 46 normally menstruating dysmenorrheic and non-dysmenorrheic women during 2 phases of the menstrual cycle. Twenty-six women provided measurements during the follicular (days 8-14) and 20 during the luteal (days 15-21) phases of the menstrual cycle. A significantly lower pain threshold was obtained during the luteal as compared to the follicular phase. Pain tolerance showed a similar but non-significant trend. Visual analog ratings were significantly lower in dysmenorrheic women during the follicular than the luteal phase. Also, these ratings were lower than those of non-dysmenorrheic women in the follicular phase. This finding may support an adaptation-levels model, in that dysmenorrheic women report less pain than do non-dysmenorrheic women because they compare cold pressor pain with internal menstrual pain.     

Hemodynamic and sympathetic nervous system responses to stress during the menstrual cycle

In this study, the impact of menstrual cycle phase on hemodynamic and sympathetic nervous system responses was examined during exposure to a battery of laboratory stressors. Participants were 40 healthy premenopausal women, aged 26 to 51. Impedance cardiography was used to measure stroke volume, heart rate, and cardiac output. Systemic vascular resistance was derived on the basis of concurrently recorded blood pressure and cardiac output. The menstrual cycle's effect on the sympathetic nervous system response was explored by evaluating plasma catecholamine responses during stress. In luteal compared with follicular subjects, systemic vascular resistance was significantly lower during all stress tasks (P < 0.03). Catecholamine responses were also significantly lower in luteal subjects (P < 0.004). The results suggest that the sympathetic nervous system may respond to stress differently during different phases of the menstrual cycle. This finding has implications for understanding "whitecoat hypertension" in women, and highlights the need to measure blood pressure during several office visits. Perhaps high blood pressure readings recorded during the follicular phase should be reexamined during the luteal phase before considering pharmacologic intervention.     

Alcohol effects on luteinizing hormone releasing hormone-stimulated anterior pituitary and gonadal hormones in women

Plasma luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin, estradiol (E2) and progesterone were measured in 24 normal, adult women before and after i.v. administration of 100 micrograms luteinizing hormone releasing hormone (LHRH; Factrel) and p.o. ingestion of an alcohol (0.694 g of alcohol per kg b.wt.) or placebo solution. Twelve subjects were studied during the early follicular phase of the menstrual cycle and 12 subjects were studied during the midluteal phase of the menstrual cycle. During each menstrual cycle phase, six subjects received placebo solution and six subjects received alcohol solution administered under double-blind conditions. Mean peak blood alcohol levels of 113 to 122 mg/dl were measured 45 to 60 min after initiation of alcohol intake. LHRH stimulated a significant increase in LH after both alcohol (P less than .0001) and placebo (P less than .0001) administration, and this LH increase was equivalent during the follicular and the luteal phases of the menstrual cycle. LHRH also stimulated a significant increase in FSH levels after both alcohol and placebo intake during the follicular and luteal phases of the menstrual cycle (P less than .0001). There were no significant differences in LHRH-stimulated FSH between the alcohol and placebo conditions. Plasma prolactin levels also increased significantly after LHRH administration during the follicular and luteal phases of the menstrual cycle (P less than .0001). There were no significant differences in prolactin response to LHRH administration between the alcohol or placebo conditions during the follicular and luteal phases of the menstrual cycle. Plasma E2 levels did not increase significantly after LHRH administration and placebo alcohol during the follicular phase of the menstrual cycle.(ABSTRACT TRUNCATED AT 250 WORDS)     

Oral contraceptives elevate core temperature and heart rate duringexercise in the heat

It is generally believed that the elevated progesterone levels seen during the lutealphase of the menstrual cycle alter thermoregulatory function during exercise. We hypothesizedthat oral contraceptives (OCs) that contain synthetic progestogen would alter thermoregulationduring exercise in a manner similar to that seen during the luteal phase. To test this hypothesis10 healthy women currently taking OCs were recruited. Subjects performed a 1 h exercise boutin the heat (30 °C, 50% relative humidity; RH) at 60% of their maximumoxygen uptake on two occasions: once while on OCs and once during a control trial when thesubjects were off OCs. Core temperature, skin temperatures, heart rate, skin blood flow andsweat rate were measured at rest and every 20 min during both exercise bouts. OCssignificantly increased core temperature and heart rate over that seen during the controlcondition. Specifically, after 1 h of exercise, OCs caused a mean 0·3 °C and an 8-bpm increase in core temperature and heart rate respectively. Additionally, the differences incore temperature and heart rate during the two trials became more exaggerated as exerciseduration increased, as evidenced by significant treatment-by-time interactions. These resultssuggest that OCs alter thermoregulatory and cardiovascular function during exercise in theheat. Furthermore, the changes in core temperature and heart rate seen during exercise whiletaking OCs are similar in direction and magnitude to those observed during the luteal phase ofthe menstrual cycle.     

Cardiovascular functioning during the menstrual cycle

Variations in cardiovascular functioning during the ‘normal’ menstrual cycle have been little researched. Resting‐blood pressures, resting‐heart rate, rate‐pressure product (RPP) and a derived index of fitness (Schneider Index) were monitored throughout natural, hormonally defined menstrual cycles. Volunteers were 26 women (20–48 years) who had regular (25–35 days) cycles. Their blood pressures and heart rate (at rest and according to Schneider’s protocol) were measured at the same time daily (Monday–Friday) for 5 weeks. Daily, early morning‐urine samples were assayed for sex hormones enabling accurate definition of cycle phase for each woman. Resting systolic‐blood pressure was significantly higher in the ovulatory phase (P<0·05) than in the follicular or luteal phases, but resting‐diastolic pressures did not differ significantly between phases. Resting‐heart rate was significantly higher in both ovulatory (P<0·01) and luteal (P<0·01) phases than in the menstrual and follicular phases. The Schneider Index was higher during the follicular phase than during the ovulatory (P<0·005) or luteal (P<0·01) phases, the RPP was higher during the ovulatory phase than during the bleeding (P<0·05) and follicular (P<0·005) phases. These findings provide a pattern of menstrual cycle‐related variation in cardiovascular functioning that can be related to established actions of the ovarian steroids.     

Changes in the dopaminergic control of prolactin secretion and in ovarian steroids in migraine

Prolactin (PRL) responses to dopamine (DA) blockers and to direct and indirect DA agonists have been studied in 23 healthy women, 17 women with catamenial migraine and 17 with non-catamenial migraine in both their follicular and luteal phases. PRL responses to the DA blockers were greater in the follicular phase of both migraine groups than in controls. The inhibitory effect of nomifensine on PRL secretion was dampened in the follicular phase of both migraine groups. These findings demonstrate an increased PRL reserve in migraine and suggest the existence of a dopaminergic supersensitivity of the lactotrophic postsynaptic DA receptors. The impaired inhibitory effect of nomifensine on PRL secretion hints at a decrease of the presynaptic DA content in tuberoinfundibular DA neurons. In migrainous women 17-beta-oestradiol levels are higher in both ovarian phases, whereas progesterone concentrations and the progesterone to oestradiol ratio are lower than in healthy subjects in the luteal phase. These data suggest the existence of a change in the oestrogen-dependent modulation of pituitary DA receptors.     

Reproducible assessment of vaginal and rectal mucosal and skin blood flow: laser doppler fluximetry of the pelvic microcirculation

Pelvic venous congestion is a common cause of chronic pelvic pain in women of reproductive age. Although this condition represents a functional disturbance of the pelvic circulation which is related to the menstrual cycle, its aetiology remains unknown. Indirect techniques demonstrate that the vasoconstrictive reflex response of the microcirculation of the foot to a rise in venous pressure is attenuated throughout the menstrual cycle. We wished to develop a simple and non-invasive direct measure of pelvic blood flow to aid diagnosis of this condition. Laser doppler blood flux measurements of the skin of the big toe and of the vaginal and rectal mucosa in the follicular and luteal phases of the menstrual cycle in 12 healthy asymptomatic premenopausal women (mean age 30 years) with regular cycles and in four healthy asymptomatic postmenopausal women (mean age 59 years) were carried out both in the supine position and in response to 40 degrees head-up tilt. The coefficient of variation of resting vaginal flux was lower for measurements in postmenopausal women (0.04) and in premenopausal women in the follicular phase (0. 07) compared with those in the luteal phase (0.16). At rest, vaginal blood flow was higher than rectal and skin flux in both premenopausal and postmenopausal women. In the follicular phase a decrease in flow was observed in response to head-up tilt in the skin (-32.0%), vagina (-34.3%) and rectum (-9.4%). In the luteal phase this reflex was attenuated at these three sites (-8.6%, +6.7% and +7.4% respectively). There were no significant reflex changes in postmenopausal women. Thus laser doppler fluximetry is a reproducible method for comparing the flux of blood in the microcirculation of the skin and of the vaginal and rectal mucosa. The skin is the least sensitive site for testing vascular reactivity in response to cyclical changes. The vaginal and rectal microcirculations are the most sensitive sites for testing visceral cyclical reactivity, and have the advantage of direct anatomical relevance. The follicular phase of the menstrual cycle is associated with greatest vascular reactivity and is the most appropriate phase during which to test for abnormal vascular responses.     

Menstrual cycle phase does not influence gender differences in experimental pain sensitivity

Influence of menstrual cycle phase on experimental pain sensitivity in women and on gender differences in pain sensitivity was examined in 48 men and 49 women in response to cold pressor, heat, and ischemic pain. Each woman was tested at three points in their menstrual cycle in randomized order, the early follicular, late follicular, and luteal phases, while men were also tested three times, controlling for number of days between test sessions. Cycle phase was confirmed via serum hormone levels. As expected, women were significantly more sensitive to cold pain (p < .01), to heat pain (p < .0001), and to ischemic pain (p < .01) than men. However, pain perception during each task was not influenced by the menstrual cycle in women, nor did the menstrual cycle influence the magnitude of the gender differences in pain sensitivity. These results indicate that although women are more sensitive to a variety of noxious stimuli than men, menstrual cycle phase does not appear to moderate those differences in healthy men and women.     

Changes of plasma total homocysteine levels during the menstrual cycle

BACKGROUND: It is known that plasma total homocysteine (tHcy) levels are lower in premenopausal and pregnant women compared with postmenopausal women. To confirm the suggestion that sex steroid hormones are nongenetic factors affecting homocysteine metabolism, we investigated the effect of natural steroid hormone levels on the fasting plasma tHcy in healthy women during the menstrual cycle. MATERIALS AND METHODS: Fifteen premenopausal women were enrolled in this study. Plasma tHcy, estradiol, progesterone and cortisol concentrations were measured in the luteal and follicular phase. The plasma tHcy concentration was determined by high performance liquid chromatography with fluorescence detection, and the steroid hormones by RIA methods. RESULTS: Mean homocysteine values increased from 7.8 micromol L-1 in the luteal phase to 8.9 micromol L-1 in the follicular phase (P < 0.000005, Student's paired t-test). We also found slight negative but insignificant correlations of homocysteine levels with estradiol in both phases of the menstrual cycle. In the case of cortisol and progesterone, no significant correlations with plasma homocysteine were found. CONCLUSION: The study provides the first evidence of significant differences in plasma homocysteine concentration during the menstrual cycle. From our observed findings it is necessary to account for the phase of the menstrual cycle when determining homocysteine in premenopausal women.     

Sudomotor and vasomotor activity during the menstrual cycle with global heating

Many studies have reported that there are changes in sympathetic activity throughout the menstrual cycle as there are oestrogen receptor in the hypothalamus and all other parts of the sympathetic nervous system. The purpose of this study was to see whether there were variations in sympathetic activity, skin vasomotor and sweat gland sudomotor rhythms during the menstrual cycle. Eight young female subjects with a regular menstrual cycle participated in the study. Subjects were tested once during the follicular phase and once during the luteal phase. Skin blood flow and sweat rate were significantly higher in the luteal phase compared with the follicular phase (p < .05), but the frequency and magnitude of sudomotor and vasomotor rhythms were significantly greater in the follicular phase (p < .05). In contrast, spectral data showed less sympathetic activity in the luteal phase. A significant finding here is that the sudomotor rhythm of sweat glands is altered by the menstrual cycle.     

Blood pressure and renal haemodynamic response to salt during the normal menstrual cycle

The purpose of the present study was to evaluate prospectively blood pressure and the renal haemodynamic response to salt during the normal menstrual cycle. A total of 35 healthy normotensive young women not on oral contraceptives were enrolled; 17 were studied in the follicular phase and 18 in the luteal phase of the menstrual cycle. The women in each group were then randomly allocated to receive a low-sodium (40 mmol/day) or a high-sodium (250 mmol/day) diet for a 7-day period in two consecutive menstrual cycles. At the end of each dietary period, 24 h ambulatory blood pressure, urinary sodium excretion, plasma renin activity, plasma catecholamine levels and renal haemodynamics were measured. Our results show that the blood pressure response to salt is comparable during the luteal and the follicular phases of the normal menstrual cycle and is characterized by a salt-resistant pattern. In the kidney, effective renal plasma flow was significantly greater and the filtration fraction lower (P<0.05) after salt loading in women studied in the luteal phase compared with women investigated in the follicular phase. This study thus demonstrates that the female hormone status does not affect the blood pressure response to sodium in young normotensive women. However, in contrast with systemic haemodynamics, the renal response to salt varies during the normal menstrual cycle, suggesting that female sex hormones play a role (direct or indirect) in the regulation of renal haemodynamics.     

Influence of the menstrual cycle on the absorption and elimination of D-xylose

Thirteen healthy female volunteers with regular menstrual cycles (28 +/- 2 days) received 25 gm oral and 5 gm intravenous doses of D-xylose on 2 successive days during the follicular, ovulatory, and luteal phases of two consecutive menstrual cycles. The ovulation time was characterized by luteinizing hormone levels, body basal temperatures, and progesterone and estradiol serum levels. D-Xylose was assayed in plasma and urine with a phloroglucinol-based colorimetric method. The findings of this study indicated that menstrual cycle did not significantly affect D-xylose absorption. After oral administration, the total clearance was significantly increased in cycle 2 during the luteal phase (p = 0.004). After intravenous administration in both cycles, D-xylose total clearance was also significantly faster during the luteal phase (p = 0.038 and p = 0.041, respectively). After oral administration, the renal clearance tended to be higher during the luteal phase in both cycles studied. After intravenous administration, this parameter was increased during the luteal phase by 24% and 25% in cycle 1 and by 8% and 12% in cycle 2. These findings are consistent with those of others showing an increase in glomerular filtration rate (GFR) during the luteal phase of the menstrual cycle. The findings of this study seem to be explained by the hormonal changes occurring during the menstrual cycle. Further investigations are warranted with use of specific probes of renal processes (GFR, renal reabsorption and tubular secretion) to confirm our findings and to elucidate the underlying mechanisms.