Chronobiological studies of plasma prolactin in women in Kyushu, Japan, and Minnesota, USA

Photoperiodic and circadian bifurcation theories of depression and mania

Seasonal effects on mood have been observed throughout much of human history.  Seasonal changes in animals and plants are largely mediated through the changing photoperiod (i.e., the photophase or duration of daylight).  We review that in mammals, daylight specifically regulates SCN (suprachiasmatic nucleus) circadian organization and its control of melatonin secretion.  The timing of melatonin secretion interacts with gene transcription in the pituitary pars tuberalis to modulate production of TSH (thyrotropin), hypothalamic T3 (triiodothyronine), and tuberalin peptides which modulate pituitary production of regulatory gonadotropins and other hormones.  Pituitary hormones largely mediate seasonal physiologic and behavioral variations.  As a result of long winter nights or inadequate illumination, we propose that delayed morning offset of nocturnal melatonin secretion, suppressing pars tuberalis function, could be the main cause for winter depression and even cause depressions at other times of year.  Irregularities of circadian sleep timing and thyroid homeostasis contribute to depression.  Bright light and sleep restriction are antidepressant and conversely, sometimes trigger mania.  We propose that internal desynchronization or bifurcation of SCN circadian rhythms may underlie rapid-cycling manic-depressive disorders and perhaps most mania.  Much further research will be needed to add substance to these theories.

Age-dependent association of serum prolactin with glycaemia and insulin sensitivity in humans

The dopamine agonist bromocriptine has been approved for the treatment of type 2 diabetes in the United States. Bromocriptine inhibits prolactin secretion, and patients with hyperprolactinaemia display impaired insulin sensitivity. We therefore hypothesized that low prolactin levels are associated with lower glycaemia and higher insulin sensitivity in healthy subjects. Prolactin levels were determined from fasting serum in participants without diabetes from the cross-sectional Tübingen family study for type 2 diabetes (m/f = 562/1,121, age = 40 ± 13 years, BMI = 30 ± 9 kg/m(2)). A 75 g oral glucose tolerance test was performed, and the area under the glucose curve (AUC(0-120)Glucose) and insulin sensitivity index were calculated. A subgroup (n = 494) underwent hyperinsulinaemic-euglycaemic clamp tests. Prolactin associated positively with insulin sensitivity (p = 0.001, adjusted for gender, age, and BMI). Age strongly interacted (p < 0.0001) with the effect of prolactin on insulin sensitivity, inverting the positive relationship to a negative one in younger participants. Glycated haemoglobin (HbA1c) and AUC(0-120)Glucose correlated negatively with prolactin, and an interaction with age was found as well. Higher prolactin levels are associated with improved insulin sensitivity and lower glucose in individuals without diabetes. This relationship turns to its opposite in younger persons. As prolactin is a proxy for the dopaminergic tone in the central nervous system, these associations may indicate an age-dependent influence of the brain on peripheral insulin sensitivity.

Menstrual cycles are influenced by sunshine

INTRODUCTION

The study determined the effect of seasons and meteorological variables on ovarian-menstrual function.

METHODS

Women (N=129) living in Novosibirsk (55°N), Russia, provided data on normal menstrual cycles for over 1 year between 1999 and 2008. Of these, 18 together with 20 other healthy women were investigated once in winter and once in summer in 2006-2009. The investigated variables included serum levels of follicle-stimulating hormone (FSH), luteinising hormone (LH) and prolactin on day ∼ 7 of the menstrual cycle, ovary follicle size (by ultrasound) on day ∼ 12 and ovulation occurrence on subsequent days.

RESULTS

In summer vs. winter, there was a trend towards increased FSH secretion, significantly larger ovarian follicle size, higher frequency of ovulation (97% vs. 71%) and a shorter menstrual cycle (by 0.9 days). LH and prolactin levels did not change. In all seasons combined, increased sunshine (data derived from local meteorological records) 2-3 days before the presumed ovulation day (calculated from the mean menstrual cycle) led to a shorter cycle length. Air/perceived temperature, atmospheric pressure, moon phase/light were not significant predictors.

CONCLUSIONS

Ovarian activity is greater in summer vs. winter in women living in a continental climate at temperate latitudes; sunshine is a factor that influences menstrual cycle.

[Use of a new protocol for prolactin extraction and reduction of false hyperprolactinemia]

INTRODUCTION

Numerous authors have reported that prolactin measurement is influenced by several factors and consequently the values obtained may not faithfully reflect the physiological reality of the individual studied. Unless a series of measures is adopted, especially in the pre-analytic stage, values may be falsely elevated. The objective of the present study was to evaluate the extent to which optimization or non-optimization of the extraction procedure translates into higher results and how reports expressed in terms of monomeric (biologically active) prolactin could be crucial to adopt a diagnosis and therapeutic approach.

MATERIAL AND METHODS

We performed two extractions in each woman (following the protocol universally used for this kind of analysis): one through direct puncture and another 60 min later without a new puncture (a catheter was inserted in the site of the first puncture and kept permeable by salinization). The monomeric fraction was then studied, if required.

RESULTS

A statistically significant difference was observed between the 2 extractions. The monomeric fraction was three times lower in the second extraction than in the first.

DISCUSSION

The results of this study justify systematic use of extraction techniques that avoid the stress of venous puncture, as well as the use of the term biologically active prolactin [monomeric (little) prolactin fraction] in reports.

Weak evidence of bright light effects on human LH and FSH

Background

Most mammals are seasonal breeders whose gonads grow to anticipate reproduction in the spring and summer. As day length increases, secretion increases for two gonadotropins, luteinizing hormone (LH) and follicle stimulating hormone (FSH). This response is largely controlled by light. Light effects on gonadotropins are mediated through effects on the suprachiasmatic nucleus and responses of the circadian system. There is some evidence that seasonal breeding in humans is regulated by similar mechanisms, and that light stimulates LH secretion, but primate responses seem complex.

Methods

To gain further information on effects of bright light on LH and FSH secretion in humans, we analyzed urine samples collected in three experiments conducted for other goals. First, volunteers ages 18-30 years and 60-75 commenced an ultra-short 90-min sleep-wake cycle, during which they were exposed to 3000 lux light for 3 hours at balanced times of day, repeated for 3 days. Urine samples were assayed to explore any LH phase response curve. Second, depressed participants 60-79 years of age were treated with bright light or dim placebo light for 28 days, with measurements of urinary LH and FSH before and after treatment. Third, women of ages 20-45 years with premenstrual dysphoric disorder (PMDD) were treated to one 3-hour exposure of morning light, measuring LH and FSH in urine before and after the treatments.

Results

Two of the three studies showed significant increases in LH after light treatment, and FSH also tended to increase, but there were no significant contrasts with parallel placebo treatments and no significant time-of-day treatment effects.

Conclusions

These results gave some support for the hypothesis that bright light may augment LH secretion. Longer-duration studies may be needed to clarify the effects of light on human LH and FSH.

Possible Linkage between the Ability to Change the Period (τ) of the Prolactin and Cortisol Rhythms in Women and Breast Cancer Risk

The 24 h profiles of plasma hormone concentrations are rhythmic. The circadian period (tau) changes in development, with seasons, and in women with different stages of the menstrual cycle. It is known that the rhythms of prolactin and cortisol are sensitive to environmental time cues, such as changes in day length and phase; however, the importance of these changes is not yet understood. This study investigates whether there is a relation between the ability of a subject to respond to external cues that are associated with seasonal changes causing alteration of the rhythm's periods in cortisol and prolactin and the epidemiologically determined susceptibility to breast cancer. It is shown that the rhythmic output pattern of prolactin and cortisol in vivo is generated by more than one oscillator and structured by more than one rhythmic component. Each cohort of American women, classified on an epidemiologic basis as high risk (HR) or low risk (LR) to develop breast cancer, expresses different rhythmic output patterns of both variables, suggesting that the genetic background as defined by the risk state is related to differences in the circadian time structure, including the ability of the subject to change the rhythm's tau. The LR cohort exhibited a statistically significant change between seasons in the rhythm's tau of both the prolactin and cortisol patterns. In contrast, the HR cohort showed no change in the rhythm's tau between seasons for prolactin and cortisol patterns. These results show that in human beings, the presence of a circannual rhythm in the circadian time structure or the ability to adapt the circadian rhythmic pattern of these variables to external cues, such as seasons, is related to the partly genetically determined risk state to develop breast cancer and may be of importance for human health.

Chronobiology in the endocrine system

Biological signaling occurs in a complex web with participation and interaction of the central nervous system, the autonomous nervous system, the endocrine glands, peripheral endocrine tissues including the intestinal tract and adipose tissue, and the immune system. All of these show an intricate time structure with rhythms and pulsatile variations in multiple frequencies. Circadian (about 24-hour) and circannual (about 1-year) rhythms are kept in step with the cyclic environmental surrounding by the timing and length of the daily light span. Rhythmicity of many endocrine variables is essential for their efficacy and, even in some instances, for the qualitative nature of their effects. Indeed, the continuous administration of certain hormones and their synthetic analogues may show substantially different effects than expected. In the design of drug-delivery systems and treatment schedules involving directly or indirectly the endocrine system, consideration of the human time organization is essential. A large amount of information on the endocrine time structure has accumulated, some of which is discussed in this review.

Higher cortisol levels in spring and fall in patients with major depression

BACKGROUND

Multiple lines of evidence suggest that there are seasonal effects on mood and behavior, and that these effects are related to serotonergic and hypothalamic-pituitary-adrenal (HPA) function. This study sought to determine whether there is a seasonal effect on clinical parameters, baseline cortisol and prolactin levels, and cortisol and prolactin responses to fenfluramine administration in subjects with major depression.

METHODS

In all, 136 subjects with major depression entered the study. Sixty-two subjects who had a major depressive episode (MDE) in Spring or in Fall (the Spring/Fall group) were compared to 74 subjects who had MDE in Winter or in Summer (the Winter/Summer group). Demographic and clinical parameters were assessed and recorded. Clinical parameters included depression, aggression, impulsivity, hopelessness, hostility, and current suicide ideation rating scales, suicide attempt status, and number and maximum lethality of suicide attempts. Cortisol and prolactin levels were drawn before fenfluramine administration and hourly for 5 h thereafter. Cortisol and prolactin levels were computed as the area under the curve of hourly cortisol measurements.

RESULTS

Baseline cortisol levels were significantly higher in the Spring/Fall group compared to the Winter/Summer group (14.1+/-4.5 ng/ml vs. 12.5+/-4.4 ng/ml, df=132, t=2.16, p=0.03). There were no seasonal effects on baseline prolactin levels, or post-challenge cortisol and prolactin levels.

CONCLUSIONS

The Spring/Fall group and the Winter/Summer group may represent different subtypes of major depression. Future studies need to both confirm our results and elucidate the mechanism of the circannual effect on biological function in depressed patients. The results of our study underline the importance of considering seasonality in psychobiology.

Seasonal variation in whole blood cytokine production after LPS stimulation in normal individuals

We examined seasonal differences in whole blood cytokine production after endotoxin (LPS) stimulation in 17 healthy individuals from an urban area having normal sleep/wakefulness pattern. We used 500 pg/ml of LPS for incubation period of 4 h to stimulate 100 microl of whole blood of the same subjects in June, September, February, and March. We found no differences in the circulating total WBCs and differentials including monocytes between different seasons. We found during September (autumn) a reduced pro-inflammatory cytokine production in terms of TNF-alpha and IL-6 production compared to the other seasons. We also found a reduced anti-inflammatory cytokine production in June (summer) and September (autumn) in terms of IL-10, TNF-RI and TNF-RII compared to February (winter) and March (spring). Our results suggest that in early summer there is a predominating pro-inflammatory cytokine response which is counterbalanced early in autumn. These results may have significant implications in the determination of reference values, in exploration of immune response and inflammatory disease prevalence between different seasons, in determining LPS tolerance (immunoparalysis) and planning clinical trials and immunomodulary therapies. However, the effect of dark/light exposure differences on the circadian periodicity in the responsiveness of immune cells during different seasons should be further investigated.

Seasonal and Biological Variation of Blood Concentrations of Total Cholesterol, Dehydroepiandrosterone Sulfate, Hemoglobin A1c, IgA, Prolactin, and Free Testosterone in Healthy Women

Background: Concentrations of physiological response variables fluctuate over time. The present study describes within-day and seasonal fluctuations for total cholesterol, dehydroepiandrosterone sulfate (DHEA-S), hemoglobin A1c (HbA1c), IgA, prolactin, and free testosterone in blood, and estimates within- (CVi) and between-subject (CVg) CVs for healthy women. In addition, the index of individuality, prediction intervals, and power calculations were derived.

Methods: A total of 21 healthy female subjects participated in the study. Using a random effects analysis of variance, we estimated CVg and total within-subject variation (CVti), i.e., the combined within-subject and analytical variation, from logarithmically transformed data. Analytical variation was subtracted from CVti to give CVi. CVi was estimated from samples taken monthly during 1 year (CViy), weekly during 1 month (CVim), and six times within 1 day (CVid).

Results: A cyclic seasonal variation was demonstrated for total cholesterol, DHEA-S, HbA1c, prolactin, and free testosterone. Within-day variation was shown for prolactin and free testosterone. The overall mean values for the group and the variability (CViy and CVg) were: 5.1 mmol/L, 5.5%, and 5.0% for total cholesterol; 6.6 μmol/L, 7.1%, and 21% for DHEA-S; 4.3%, 2.6%, and 3.3% for HbA1c/hemoglobintotal; 2.1 g/L, 5.9%, and 13% for IgA; 136 mIU/L, 23%, and 27% for prolactin; and 5.4 pmol/L, 21%, and 29% for free testosterone.

Conclusions: Collecting samples at specific hours of the day or times of the year may reduce high biological variation. Alternatively, the number of individuals may be increased and a paired study design chosen to obtain adequate statistical power.

Biologic rhythms in the immune system

In all of its components, the immune system shows regularly recurring, rhythmic variations in numerous frequencies; the circadian (about 24 h) rhythms are the best explored. The circadian variations in immunocompetent cells circulating in the peripheral blood are of a magnitude to require attention in medical diagnostics. Both the humoral arm and the delayed (cellular) arm of the immune system function in a rhythmic manner. The response of the immune system to introduction of an antigen and to challenge of the sensitized organism varies in extent in the circadian frequency range and also in lower frequencies, for example, of about a week (circaseptan) or seasonally (circannual). The medical application of the biologic rhythms of the immune system extends to diagnostic measures, as well as treatment.

Prolactin: the forgotten hormone of human breast cancer

Prolactin (PRL) is both a mitogen and a differentiating agent in the mammary gland. It has been shown to be involved in mammary cancer development in rodents, but in human breast cancer, its role has long been overlooked. Three criteria are applied to demonstrate PRL's involvement in this disease: (1) PRL receptors are present in human breast cancer cells, (2) human breast cancer cells in culture respond to PRL as a mitogen, and (3) PRL is synthesized by human breast cancer cells and inhibition of the binding of PRL to its receptors inhibits cell growth.

Modifications of circadian and circannual rhythms with aging

Whereas biological rhythms are now fairly well documented in young healthy adults, reports in elderly are relatively few for obvious reasons, including the difficulty of setting groups matched in age, sociological and professional background, medical history, and not in need of specific medication. Aging may modify one or several parameters characterizing biological rhythms. The modifications are different from one function to the next, and great care should be given not to mistake changes attributable to the aging process with those resulting from physical and physiological impairment caused by passed environmental aggressions and diseases. Nevertheless, the increasing number of subjects reaching the age of 65 or older, thanks to medical progress, makes necessary establishing time-qualified references values in the aged, as this kind of investigation should lead to an improvement of the conditions and quality of life of elderly subjects.

Seasonal variation in postdexamethasone cortisol values in depressed inpatients. Results of least squares cosine spectral analysis

Recently, a significant seasonal variation in postdexamethasone (post-DST) cortisol values in depressed patients has been reported. This study aimed to investigate seasonal variation in post-DST cortisol values in 269 depressed patients admitted to a psychiatric ward during 70 consecutive months. By means of analysis of variance no significant differences could be detected in post-DST values in depressed men or women, alone or together, between the 12 months, the period November-February versus March-October, or between the tour quartiles. By means of spectral analysis no significant seasonal rhythms, i.e. annual or harmonic rhythms, could be found in the time series of post-DST cortisol values either in the total group of depressed patients or in depressed women separately (n = 190). Spectral analysis showed a significantly biannual rhythm in the post-DST cortisol values in depressed men, with peaks in June and December and troughs in March and September. This biannual rhythm explained 12.4% of the variance in the post-DST cortisol values of depressed men. The results show that there is a significant seasonal variation in post-DST cortisol values in depressed men, but not in depressed women.

Seasonal variation in the secretion of mammotrophic hormones in normal women and women with previous breast cancer

Hormones such as melatonin whose serum concentrations vary seasonally have been previously implicated in the growth of breast cancer. The present study was undertaken to identify possible seasonal variation in a range of mammotrophic hormones which could exert a chronobiologic influence in women with breast tumours. Fifteen premenopausal women with a history of previous breast cancer (BC subjects) and 10 control women underwent 2-hourly serum sampling for 24 h at both summer and winter solstice for measurement of melatonin, growth hormone (GH), insulin-like growth factor-I (IGF-I), cortisol, prolactin and thyrotrophin (TSH). Hormone secretion at the different seasons was compared by measuring the area under the 24 h serum hormone concentration x time curves and by time series analysis of summer-to-winter differences in hormone concentration. Control women had significantly higher GH and IGF-I levels in summer compared to winter and significantly higher cortisol secretion in winter than summer. In contrast, BC women had no significant seasonal difference in IGF-I concentrations and had a reversal of the normal seasonal pattern of melatonin secretion, although seasonal changes in GH production were similar to controls. Prolactin and TSH showed no significant summer/winter variation in either group. Thus, seasonal variations in hormone secretion seen in normal women were, with exception of GH, absent or reversed in women with a previous history of breast cancer. As a result these individuals may be exposed to an asynchronous hormonal stimulus which could influence tumour growth. These changes could reflect a constitutional abnormality in BC women or may have been induced by the previous breast tumour.

The pattern of hormonal circadian time structure (acrophase) as an assessor of breast-cancer risk

Through many hormones are secreted in a pulsatile manner, their secretion pattern can be superimposed by a 24-hour sinusoidal curve. The sinusoidal curve is then characterized by the estimated peak clock time location (acrophase), the adjusted mean (mesor) and the amplitude. When the distribution of the acrophases of 12 hormones was compared among women with regard to their age and to the level of risk of developing breast cancer, statistically significant differences were revealed between distribution patterns of acrophases of women with high (n = 12 and 45 circadian profiles) or low (n = 12 and 41 circadian profiles) risk of developing breast cancer. However, when the amplitude/mesor ratios of the corresponding hormonal rhythms were analyzed, significant differences occurred between age groups rather than between risk levels. These observations suggest that the endocrine time structure between individual women can be used as an assessor of breast-cancer risk.

Season of tumour detection influences factors predicting survival of patients with breast cancer

The rate of initial detection of breast tumours varies during the year in a seasonal fashion, more tumours being discovered in late spring/early summer than at other times of the year. This phenomenon is particularly pronounced in young women (less than 50 years) with progesterone receptor positive tumours. The present study investigates whether season of tumour detection influences the predictive capacity of several recognised prognostic and risk factors in patients with breast cancer. Axillary nodal status, tumour progesterone receptor status, and season of tumour detection significantly influenced survival in both older (greater than 50 yrs) and younger (less than 50 yrs) patients. Parity, lactational history, body mass index, tumour oestrogen receptor status, and patient age also influenced survival, but these effects were significant only in age groups less than 50 or greater than 50 yrs. Season of detection of tumour did not effect the prognostic significance of axillary nodal status. However, the effect of oestrogen receptor status on survival was more significant in patients who detected their tumours in the spring/summer compared with winter (odds ratio 0.52 and 0.73 respectively). Negative progesterone receptor status was associated with significant poorer survival only in patients with tumours found in the winter. There was a significant survival disadvantage for nulliparous compared with parous women with breast cancer who were greater than or equal to 50 years at diagnosis, and for women who had never lactated compared with those who had lactated, but this disadvantage was restricted to those who found their tumours in the summer. An increased body mass index (greater than or equal to 28) was associated with decreased survival, but this was significant only for those detecting tumours in winter. The increased incidence of detection of breast cancer in spring/summer may reflect cyclic influences on tumour growth. Such influences may be hormonal in nature and may underlie the effect of season of tumour detection on the prognostic influence of lactation, parity, body mass index, and oestrogen and progesterone receptor status in patients with breast cancer.

Photoperiod influences the growth of colon cancer in mice

We have developed a mouse colon adenocarcinoma cell line that produces tumors in a dose-dependent manner when injected subcutaneously. Our previous work has demonstrated its sequential pattern of tumor area and weight under 12L:12D (12 hours light, 12 hours darkness) photoperiod. This study investigated whether shorter (6L:18D) or longer (18L:6D) photoperiods alter tumor growth. Significantly greater tumor area, weight, and group mortality were found in mice exposed to 12L:12D photoperiods as compared to either 6L:18D or 18L:6D photoperiods, and difluoromethylornithine (DFMO) was a more effective inhibitor of tumor growth under the 6L:18D photoperiod compared to 12L:12D. These results demonstrate an important role of photoperiod on tumor growth.

Seasonal variations in prolactin levels in schizophrenia

As part of an ongoing longitudinal study of drug-free schizophrenic patients, we serially sampled resting early morning prolactin levels in 10 subjects. In a preliminary analysis, these levels were compared to those found in matched normal control subjects over a 4-year period. Both control and schizophrenic subjects showed a marked annual variation in prolactin levels. Six schizophrenic patients sampled in each quarter of the year showed a significant annual rhythm, with prolactin highest in the spring (March-May). In seven schizophrenic patients and nine controls sampled at two seasons in the year, prolactin was significantly higher in spring-summer (March-August) than in fall-winter (September-February), with no difference between patients and control subjects.

Assays for prolactin: guidelines for the provision of a clinical biochemistry service

This paper summarises the views of the authors on the provision of a prolactin assay service. We discuss the pathophysiology of prolactin secretion and the clinical indications that arise from that. We cover the rather complex issue of the definition of normal and elevated prolactin levels. From these considerations, certain guidelines on the analytical performance of prolactin assays and their provision in a clinical biochemistry service are given. The extent to which currently available methods and performance as revealed by the UK External Quality Assessment Scheme (EQAS) match these guidelines are described and certain conclusions are reached. Finally, probable future developments are briefly discussed. The main conclusions and recommendations are as follows: Reagents of appropriate quality are available to enable prolactin immunoassays to be provided in UK clinical biochemistry laboratories. These are provided either separately or in the form of kits from both commercial and NHS sources. There is no requirement for individual laboratories to undertake their own antiserum production or prolactin iodination. Acceptable performance (as defined using internal QC procedures and the UK EQAS) is achievable using these reagents/kits, although one commercial kit shows a consistent marked negative bias. Reference ranges, including 'normal ranges', show considerable between-centre variability. Many centres have not established their own ranges, even those using in-house methods. Reference ranges for use in clinical biochemistry laboratories are proposed in this report. Some general guidance on the provision of a prolactin service is given, although this does not differ in principle from that appropriate for other peptide hormone analytes. There is no evidence that centres with small workloads perform any worse than average, although it may be more cost-efficient for such centres to send the samples elsewhere. As with other peptide analytes, non-isotopic immunometric methodology is likely to replace current radioimmunoassay methods in the near future.

Plasma hormones in parous, nulliparous and postmenopausal Japanese women

Mechanisms associated with protection against breast cancer in parous women with an early pregnancy are unknown. Elevated or deficient steroid hormone levels or dysfunctional release of prolactin have been postulated. Since these effects have not been reported in low-risk Japanese women, we have compared the hormone levels in age-weight-risk factor matched premenopausal nulliparous and parous Japanese women with established menstrual regularity. Higher luteal phase plasma levels of estradiol and estrone occurred in parous versus nulliparous women, while plasma prolactin and androgen levels were unaltered. It is suggested that the higher estrogen and lower LH levels, as in short versus long menstrual cycles, results from failure of the opioid GnRH. LH axis to return to pre-pregnancy levels.

Diurnal variations in prolactin and growth hormone levels in normal premenopausal vegetarian and omnivorous women

Diurnal levels of plasma prolactin and growth hormone were measured in 47 normal premenopausal women, 26 of whom were established vegetarians and 21 of whom were omnivorous controls. There were no differences between the median prolactin levels of the two groups during a 24-hour period of investigation. When the groups were further subdivided into ovolactovegetarians and vegans, still no differences were found in prolactin secretion. In contrast, the vegetarian women exhibited elevation of growth hormone levels during the period of study, which was particularly marked at midnight and 10 A.M.

Circadian characteristics of urinary epinephrine and norepinephrine from healthy young women in Japan and U.S.A

Clinically healthy diurnally active young adult women were studied during the same season (March) at the Universities of Kyushu (Fukuoka City, Japan) and of Minnesota (Minneapolis, U.S.A.), under comparable conditions, except that the habitual diets were not changed. The subjects (20 Japanese and 16 Americans of mixed Caucasian background) were studied over a single 24-hr span. Urine was collected at 4-hr intervals. A circadian rhythm in total urinary norepinephrine excretion showed similar characteristics in Japanese and Americans. In epinephrine excretion, the Japanese women showed a statistically significantly higher amplitude with higher peak values, but no statistically significant difference in the rhythm-adjusted mean. This intergroup difference is strictly time dependent; it does not come to the fore in urine samples covering the nocturnal rest span of the subjects.

Circannual rhythms of plasma growth hormone, thyrotropin and thyroid hormones in prepuberty

To clarify the occurrence of circannual GH, TSH, T4 and T3 rhythms in prepuberty we have been studying, for a four year period, 150 healthy subjects, aged 6-10, by cross-sectional design. Plasma samples were taken at 0800 h and all hormones were measured by RIA. The occurrence of any circannual rhythm was statistically investigated by the cosinor method. A significant rhythm was validated (P = 0.02) only in TSH secretion, with annual crest time in December; GH, T4, T3 did not show a circannual rhythm. Our results seem to strengthen the hypothesis that the thyroid hormones, at least before puberty, do not play an important role in the regulation of circannual TSH periodicity.

Seasonal variation in human central dopamine activity

This report focuses on two studies of seasonal variation of central dopamine activity in patients with schizophrenia and normal controls. In the two investigations, data were grouped and analyzed by season (i.e., spring-summer vs. fall-winter). The first study concerned blink rate, a putative measure of central dopamine activity; the blink rate for patients with schizophrenia was significantly increased during the spring-summer period. In the second study concentrations of catecholamines and their metabolites were measured in the hypothalamus and nucleus accumbens of normal and schizophrenic subjects. Findings include a reduced concentration of hypothalamus dopamine in normal controls and a reduced concentration of homovanillic acid in the nucleus accumbens of patients with schizophrenia, both during the spring-summer period.

Circannual variation of intestinal cell proliferation in BDF1 male mice on three lighting regimens

BDF1 male mice were studied over a 24-hr span in winter, spring, summer and fall. For three weeks prior to study, one-third of the animals were kept under a lighting regimen of 8 hr light alternating with 16 hr of darkness (LD 8:16), one-third on a lighting regimen of LD 12:12 and a remainder on a lighting regimen of LD 16:8. During each study, subgroups of animals on all three lighting regimens were killed at 4-hr intervals over a 24-hr span. Twenty minutes prior to being killed, the animals received 5 microCi of [3H]-thymidine/0.2 ml/20 gm of body weight intraperitoneally. The thymidine uptake in the DNA of the colon and of the small intestine were studied as an index of cell proliferation. A circadian rhythm in [3H]-thymidine uptake in the colon was found and validated by cosinor analysis. This rhythm was similar in acrophase and amplitude in the animals kept on LD 8:16 and LD 12:12. Also in the mice on LD 16:8, there was a statistically significant circadian rhythm of [3H]-thymidine uptake in the DNA of the colon during all four seasons. The acrophases of this rhythm, however, varied widely suggesting free running. A circadian rhythm of [3H]-thymidine uptake in small intestine was less consistent. In animals on all three lighting regimens, however, a circannual variation of [3H]-thymidine uptake in DNA in colon and small intestine was found with the highest uptake during summer. This study indicates that a lighting regimen of LD 16:8 does not reliably synchronize the circadian rhythm of [3H]-thymidine uptake in the colon. It further shows a circannual rhythm of this function in the colon and in the small intestine which persists under three lighting regimens (LD 8:16, 12:12 and 16:8) maintained for three to four weeks prior to being killed.

Circadian and circannual rhythms of hormonal variables in elderly men and women

A group of fourteen men (73 +/- 5 yr of age), and eighteen women (77 +/- 7 yr of age) institutionalized at the Berceni Clinical Hospital, Bucharest, Romania, were studied over a 24-hr span once during each season (winter, spring, summer and fall). All subjects followed a diurnal activity pattern with rest at night and ate three meals per day with breakfast at about 0830, lunch at about 1300 and dinner at about 1830. The meals were similar, although not identical for all subjects during all seasons. On each day of sampling blood was collected at 4-hr intervals over a 24-hr span. Seventeen hormonal variables were determined by radioimmunoassay. Statistically significant circadian rhythms were detected and quantitated by population mean cosinor analysis in pooled data from all four seasons in both sexes for ACTH, aldosterone, cortisol, C-peptide, dehydroepiandrosterone-sulfate (DHEA-S), immunoreactive insulin, prolactin, 17-OH progesterone, testosterone, total T4 and TSH. In women, estradiol and progesterone also were determined and showed a circadian rhythm during all seasons. Total T3 and FSH showed circadian rhythm detection by cosinor analysis in the men only; LH showed no consistent circadian rhythm as group phenomenon in men or women. A circannual rhythm was detected using the circadian means of each subject at each season as input for the population mean cosinor in the women for ACTH, C-peptide, DHEA-S, FSH, LH, progesterone, 17-OH progesterone and TSH. In the men, a circannual rhythm was detected for ACTH, FSH, insulin, LH, testosterone and T3. There were phase differences between men and women in ACTH, FSH and LH. In those functions in which both the circadian and circannual rhythms were statistically significant, a comparison of the amplitudes showed in the women a higher circannual rather than circadian amplitude for DHEA-S. In 17-OH progesterone, TSH and C-peptide, the circadian amplitude in women was larger. In men, the circannual amplitude of T3 was larger than the circadian amplitude and in insulin the circadian amplitude was larger than the circannual amplitude. There was no statistically significant difference between the circadian and circannual amplitudes in the women in ACTH and progesterone and in the men in ACTH and testosterone.

Time-related behaviour of endocrine secretion: circannual variations of FT3, cortisol, HGH and serum basal insulin in healthy subjects

Four healthy young male volunteers were submitted to the study of circadian and circannual bioperiodicities of several hormones: FT3, FT4, cortisol, HGH, prolactin, PTh and plasma insulin levels. They were observed for a whole year and their blood samples were collected six times a day, every other month. The results were analyzed by two-way ANOVA macroscopic analysis and Student t-test. Our data registered a circannual variation in the mean circadian plasma levels of the following hormones: cortisol (peak in December), HGH (peak in April), FT3 (peak in April), insulin (peak in February). FT4, prolactin and PTH showed no cyclic variation during the period of observation.

Quo vadis basic and clinical chronobiology: promise for health maintenance

Chronobiology is the eminently interdisciplinary science of interactions in time among metabolic, hormonal, and neuronal networks. It involves anatomy, biochemistry, microbiology, physiology, and pharmacology, at the molecular, intracellular, intercellular, and still higher levels of organization. The compounds coordinating a time structure--proteins, steroids, and amino-acid derivatives--provide for the scheduling of interactions among membrane, cytoplasmic, and nuclear events in a network involving rhythmic enzyme reactions and other intracellular mechanisms. The integrated temporal features of the processes of induction, repression, transcription, and translation of gene expression remain to be mapped in relation to the available framework, consisting of the sequences of phospholipid and RNA labeling, DNA formation, and mitosis, to delineate a circadian cell cycle upon which further hormonal and neural coordination acts (Halberg et al., 1959a,b, 1979a). There is a need for communication over temporal as well as spatial distances among different specialized structures devoted, in individuals, to metabolism, growth, reproduction, and the ability to adjust, and, in species, to the capacity to adapt. For a better understanding at all levels of behavior in its broader sense of organization in time, chronobiology requires familiarity with temporal aspects of metabolism, hormones, and neurons. In other words, broadly trained, full-time "general practitioners" of a chronobiology in its own right are needed.

Circannual rhythms of plasma luteinizing hormone, follicle-stimulating hormone, testosterone, prolactin and cortisol in prepuberty

For a period of four years we have been studying 106 healthy males and 66 healthy females, aged 6-10, by cross-sectional design, to look for evidence of a circannual rhythm in LH, FSH, testosterone, PRL, and cortisol secretion. Plasma samples were taken at 0800 h and all hormones were measured by RIA. A cosine function was fitted to the single data to indicate any significant circannual (about 1 year) rhythm and to estimate its parameters: mesor, amplitude, and acrophase. Annual changes were validated in the secretion of: LH (annual crest time in January in both sexes), testosterone (studied only in males, annual crest time in July), and PRL (significant rhythm only in females with annual crest time in March). FSH and cortisol did not show an annual rhythm in both sexes. Our data suggest that sex influences the circannual hormonal rhythms from prepuberty onwards.

The role of estrogens in mastopathy and mammary cancer in perimenopausal women

Fibrocystic disease of the breast (FCD) is an exaggeration of the normal physiologic response to cyclic estrogen and progesterone stimulation. The disorder can persist, with much less severity, in the menopausal woman. Whether FCD predisposes to mammary cancer remains moot. A new steroidal agent, danazol, can eliminate nodosities in the majority of women with FCD. Thermography may identify women who are at greater risk because of increased heat production. Mammography should be employed in women with persistently abnormal thermograms, even though no suggestive breast masses are palpable. Needle biopsy or surgical biopsy should be undertaken whenever a firm indurated mass is palpated, regardless of negative findings with a thermogram or mammogram. In a series of 1548 women treated for 10,715 women-years, the incidence of breast cancer after prolonged estrogen therapy was not increased. Although estrogens and prolactin have been incriminated in the etiology of mammary cancer, no hard facts exist to confirm such allegations.

Circadian rhythmicity of prolactin secretion in elderly subjects: changes during bromocriptine treatment

Prolactin has been taken as an index of neuroendocrine function in aging, where dopaminergic neurotransmission in considered to be impared. The mean concentration of the hormone in the 24 h is higher in the aged men than in the adult controls. A sleep entrained periodicity is present in both aged subjects and controls, but a harmonic analysis of rhythmicity shows that secretory episodes have in aged men a slower periodicity than in adults. In aged men bromocriptine decreases the mean PRL values in the 24 h and the periodicity analysis shows the occurrence of harmonics with shorter period.

Circadian aspects of serum prolactin and TSH lowering by bromocriptine in patients with prostatic hypertrophy

Bromocriptine mesylate lowers the serum concentration of prolactin and TSH in patients with prostatic hypertrophy as a function of drug administration time. The effect of a 2.5-mg dose in lowering these two hormones in presumably similar patients is statistically highly significant and relatively large at unusual test times (in the evening); at other, conventional test or administration times (early morning or midday), it is smaller, questionable, or not demonstrable with the dose and conditions used. Dosing without timing may lead to reduced effect or lack of effect, ambiguity and controversy, and lack of timing may account for the circumstance that an effect of bromocriptine upon TSH in human serum was not previously established. Rigorous assessment of the effect of bromocriptine mesylate upon circulating TSH and prolactin requires consideration of the entire spectrum of rhythms, ultradian and infradian as well as circannual. The circadian approach here analyzed represents a step toward that goal and indicates that the circadian frequency is a critical determinant of this response. Manipulation of TSH concentration in serum, in turn, is of interest in view of the demonstrated alteration of the circannual TSH rhythm in patients with prostatic cancer.