The relationship between blood prolactin levels and risk of breast cancer in premenopausal women

The Interplay Between Prolactin and Reproductive System: Focus on Uterine Pathophysiology

Over the last years, increasing evidence has focused on crucial pathogenetic role of PRL on malignant, premalignant and benign uterine diseases. Studies in animals and humans have documented that PRL receptors (PRL-Rs) are widely expressed on uterine cells and that PRL is directly synthesized by the endometrium under the stimulatory action of progesterone. Uterine PRL secretion is finely modulated by autocrine/paracrine mechanisms which do not depend on the same control factors implied in the regulation of PRL secretion from pituitary. On the other hand, PRL is synthesized also in the myometrium and directly promotes uterine smooth muscle cell growth and proliferation. Therefore, PRL and PRL-Rs appear to play an important role for the activation of signaling pathways involved in uterine cancers and preneoplastic lesions. Circulating PRL levels are reportedly increased in patients with cervical or endometrial cancers, as well as uterine premalignant lesions, and might be used as discriminative biomarker in patients with uterine cancers. Similarly, increased PRL levels have been implicated in the endometriosis-induced infertility, albeit a clear a causative role for PRL in the pathogenesis of endometriosis is yet to be demonstrated. This evidence has suggested the potential application of dopamine agonists in the therapeutic algorithm of women with malignant, premalignant and benign uterine lesions. This review focuses on the role of PRL as tumorigenic factor for uterus and the outcome of medical treatment with dopamine agonists in patients with malignant and benign uterine disease.

Prolactin and human weight disturbances: A puzzling and neglected association

Weight gain at the outset of prolactinomas in many women is well documented. Yet, this symptom is absent from the clinical descriptions of the disease in textbooks and reviews. This omission is almost certainly due to the absence of a physiological explanation for the phenomenon, as prolactin is not a recognized fat promoting hormone. In this review we present the clinical evidence for a relationship between prolactin and fat accumulation and address some possible mechanisms involved. We put forward the hypothesis that prolactin is a component of a neuroendocrine program - maternal subroutine - aimed at optimizing the care of the young through the production of milk, promotion of maternal behavior and increase in the metabolic efficiency of the mother. These adaptations can enable her to face the extraordinary metabolic expenses of pregnancy and nursing, especially during times of suboptimal environmental conditions. We emphasize the uniqueness of prolactin in that it is a hormone that is tonically inhibited and which has its major effects on the regulation of an inter-individual (the mother - offspring dyad), rather than an intra-individual, system. This approach opens a window to consider the possibility of external events as regulators of this system. It also allows addressing a variety of hitherto unexplained findings reported in the literature. Examples include: association of prolactinomas with paternal deprivation and with stressful life events; pseudocyesis; acute life event-driven episodes of galactorrhea; episodes of rapid weight gain following a life event; prolactin surges (without associated cortisol surges) following some psychological stresses.

Bioactive prolactin levels and risk of breast cancer: a nested case-control study

BACKGROUND

Prolactin is a lactogenic hormone associated with breast cancer risk in prospective studies, which used immunoassays. The immunoassay captures multiple isoforms and may not fully reflect the biologic activity of prolactin relevant to breast carcinogenesis.

METHODS

We considered plasma bioactive prolactin levels measured by the Nb2 lymphoma cell bioassay, which is sensitive to the somatolactogenic activity of prolactin and growth hormone, within a nested case-control study of invasive breast cancer in the Nurses' Health Studies (NHS/NHSII). We also considered associations with breast cancer risk factors.

RESULTS

We had bioassay measures on 1,329 cases and 1,329 controls. Bioassay levels were inversely associated with parity (4+ vs. 0 children = -18%, P = 0.01), body mass index (30+ vs. <22 kg/m(2) = -16%, P < 0.01), and age at menopause (53+ vs. 48 years = -18%, P = 0.03) and positively with family history of breast cancer (yes vs. no = 14%, P < 0.01). The relative risk (RR) comparing the top versus bottom quartile of bioassay levels was 1.19 [95% confidence intervals (CI), 0.94-1.51; Ptrend = 0.18]. The association was suggestively stronger for postmenopausal (RR = 1.36; 95% CI, 0.93-1.98; Ptrend = 0.12) versus premenopausal women (RR = 0.99; 95% CI, 0.71-1.37; Ptrend = 0.71). There was an association for cases diagnosed <4 years after blood draw (RR = 2.66; 95% CI, 1.45-4.89; Ptrend < 0.01), but not for cases diagnosed later. We did not observe differential associations by estrogen receptor status or other tumor characteristics.

CONCLUSIONS

Our results show similar associations for prolactin levels measured by bioassay and by immunoassay with both breast cancer risk factors and risk.

IMPACT

Future work examining risk prediction model of breast cancer can use the immunoassay to accurately characterize risk.

A prospective population-based cohort study of lactation and cardiovascular disease mortality: the HUNT study

Background

Recent studies suggest that lactation has long-term effects on risk for cardiovascular disease in women, but the effects on cardiovascular mortality are less well known.

Method

In a Norwegian population-based prospective cohort study, we studied the association of lifetime duration of lactation with cardiovascular mortality in 21,889 women aged 30 to 85 years who attended the second Nord-Trøndelag Health Survey (HUNT2) in 1995–1997. The cohort was followed for mortality through 2010 by a linkage with the Cause of Death Registry. Adjusted hazard ratios (HR) for death from all causes and cardiovascular disease were calculated using Cox regression.

Results

During follow-up, 1,246 women died from cardiovascular disease. Parous women younger than 65 years who had never lactated had a higher cardiovascular mortality than the reference group of women who had lactated 24 months or more (HR 2.77, 95% confidence interval [CI]: 1.28, 5.99). There was some evidence of a U-shaped association, where women who reported lactating 7–12 months had a HR of 0.55 (95% CI: 0.27, 1.09). No clear associations were observed among women 65 years or older.

Conclusions

Excess cardiovascular mortality rates were observed among parous women younger than 65 years who had never lactated. These findings support the hypothesis that lactation may have long-term influences on maternal cardiovascular health.

Circulating prolactin levels and risk of epithelial ovarian cancer

PURPOSE

Indirect evidence from experimental and epidemiological studies suggests that prolactin may be involved in ovarian cancer development. However, the relationship between circulating prolactin levels and risk of ovarian cancer is unknown.

METHODS

We conducted a nested case-control study of 230 cases and 432 individually matched controls within three prospective cohorts to evaluate whether pre-diagnostic circulating prolactin is associated with subsequent risk of ovarian cancer. We also assessed whether lifestyle and reproductive factors are associated with circulating prolactin among controls.

RESULTS

Prolactin levels were significantly lower among post- versus pre-menopausal women, parous versus nulliparous women, and past versus never users of oral contraceptives in our cross-sectional analysis of controls. In our nested case-control study, we observed a non-significant positive association between circulating prolactin and ovarian cancer risk (OR(Q4vsQ1) 1.56, 95 % CI 0.94, 2.63, p trend 0.15). Our findings were similar in multivariate-adjusted models and in the subgroup of women who donated blood ≥5 years prior to diagnosis. We observed a significant positive association between prolactin and risk for the subgroup of women with BMI ≥25 kg/m(2) (OR(Q4vsQ1) 3.10, 95 % CI 1.39, 6.90), but not for women with BMI <25 kg/m(2) (OR(Q4vsQ1) 0.81, 95 % CI 0.40, 1.64).

CONCLUSIONS

Our findings suggest that prolactin may be associated with increased risk of ovarian cancer, particularly in overweight/obese women. Factors associated with reduced risk of ovarian cancer, such as parity and use of oral contraceptives, were associated with lower prolactin levels, which suggests that modulation of prolactin may be a mechanism underlying their association with risk.

Duration of lactation and incidence of maternal hypertension: a longitudinal cohort study

Never or curtailed lactation has been associated with an increased risk for incident hypertension, but the effect of exclusive breastfeeding is unknown. The authors conducted an observational cohort study of 55,636 parous women in the US Nurses' Health Study II. From 1991 to 2005, participants reported 8,861 cases of incident hypertension during 660,880 person-years of follow-up. Never or curtailed lactation was associated with an increased risk of incident hypertension. Compared with women who breastfed their first child for ≥12 months, women who did not breastfeed were more likely to develop hypertension (hazard ratio (HR) = 1.27, 95% confidence interval (CI): 1.18, 1.36), adjusting for family history and lifestyle covariates. Women who never breastfed were more likely to develop hypertension than women who exclusively breastfed their first child for ≥6 months (HR = 1.29, 95% CI: 1.20, 1.40). The authors found similar results for women who had never breastfed compared with those who had breastfed each child for an average of ≥12 months (HR = 1.22, 95% CI: 1.13, 1.32). In conclusion, never or curtailed lactation was associated with an increased risk of incident maternal hypertension, compared with the recommended ≥6 months of exclusive or ≥12 months of total lactation per child, in a large cohort of parous women.

Autoantibodies to aberrantly glycosylated MUC1 in early stage breast cancer are associated with a better prognosis

Introduction

Detection of serum biomarkers for early diagnosis of breast cancer remains an important goal. Changes in the structure of O-linked glycans occur in all breast cancers resulting in the expression of glycoproteins that are antigenically distinct. Indeed, the serum assay widely used for monitoring disease progression in breast cancer (CA15.3), detects a glycoprotein (MUC1), but elevated levels of the antigen cannot be detected in early stage patients. However, since the immune system acts to amplify the antigenic signal, antibodies can be detected in sera long before the antigen. We have exploited the change in O-glycosylation to measure autoantibody responses to cancer-associated glycoforms of MUC1 in sera from early stage breast cancer patients.

Methods

We used a microarray platform of 60mer MUC1 glycopeptides, to confirm the presence of autoantibodies to cancer associated glycoforms of MUC1 in a proportion of early breast cancer patients (54/198). Five positive sera were selected for detailed definition of the reactive epitopes using on chip glycosylation technology and a panel of glycopeptides based on a single MUC1 tandem repeat carrying specific glycans at specific sites. Based on these results, larger amounts of an extended repertoire of defined MUC1 glycopeptides were synthesised, printed on microarrays, and screened with sera from a large cohort of breast cancer patients (n = 395), patients with benign breast disease (n = 108) and healthy controls (n = 99). All sera were collected in the 1970s and 1980s and complete clinical follow-up of breast cancer patients is available.

Results

The presence and level of autoantibodies was significantly higher in the sera from cancer patients compared with the controls, and a highly significant correlation with age was observed. High levels of a subset of autoantibodies to the core3MUC1 (GlcNAcβ1-3GalNAc-MUC1) and STnMUC1 (NeuAcα2,6GalNAc-MUC1) glycoforms were significantly associated with reduced incidence and increased time to metastasis.

Conclusions

Autoantibodies to specific cancer associated glycoforms of MUC1 are found more frequently and at higher levels in early stage breast cancer patients than in women with benign breast disease or healthy women. Association of strong antibody response with reduced rate and delay in metastases suggests that autoantibodies can affect disease progression.

Pregnancy and lactation after breast cancer elevate plasma prolactin, do not shorten and may prolong survival

The affliction of breast cancer is doubled for young patients wishing to have a child. Because estrogens can cause breast cancer and its elevation during pregnancy, clinical advice historically restricted pregnancy to at least 5 years post-diagnosis. Opposing evidence gradually relaxed this. Furthermore, in the last decade it was clarified that overall, post-treatment pregnancy and breast-feeding do not shorten survival. Despite this evidence and patients such as S.B. (deceased) and remarkable L.H. (five children, starting immediately after treatment for node-positive breast cancer), much opposition and restrictive advice remain: additional therapy preferred over pregnancy. In healthy women, pregnancy reduces (cause unknown) the risk of breast cancer and lactation may reduce it. These are accompanied by highly elevated plasma prolactin (PRL) over many months (pregnancy, 15-25 x daily mean 10 ng/ml; lactation, up to 30 x daily mean). PRL concentration too increases in other natural and non-biological conditions, also apparently without increasing breast cancer incidence. Nevertheless, firm and implied support for early pregnancy (and lactation) post-diagnosis and treatment may face a new issue. Over a decade, some studies have claimed epidemiological evidence that a relatively minute PRL elevation (from zero to 0.6-0.8 ng/ml) over mean level increases the risk of breast cancer (i.e. it is a carcinogen) and that this supports (and is supported by) a similar view from some laboratory research. This two-pronged mutuality could create further anxiety and unjustified advice dashing the wish for a child. Is this justified? Epidemiology on PRL and breast cancer risk in the eighties/nineties was contradictory and inconclusive; in the last decade, it was also biologically implausible. 'Positive' laboratory results targeting a 'tamoxifen for PRL' have over-shadowed confounding, negative (often called 'inconsistent') laboratory evidence. Increasingly evident complexity of conflicting biochemical, hormonal, cellular and tissue interactions, confused further by failure of molecular genetics to confirm PRL as a carcinogen, make this target more a mirage than an oasis. While recognizing the value of laboratory research primarily for facts, future progress will be most sound and rapid from observation starting with the human entity, not with its parts. Molecular genetics makes this possible and will be the epicentre of breast cancer research. Meanwhile, young breast cancer patients after initial treatment and eager for a child can today reasonably benefit from advice based on phenomena evolved over eons: pregnancy, lactation and accompanying highly-elevated PRL will not increase risk of recurrence and will in some cases prolong survival.

The effects of hyperprolactinemia on bone and fat

Many patients with prolactin secreting pituitary tumors have decreased bone mineral. The bone loss is associated with an increase in bone resorption and is secondary to prolactin-induced hypogonadism. In both sexes trabecular bone in the spine and hip is more affected than cortical bone in the distal radius. Normalization of prolactin and restoration of gonadal function increases bone density but is not associated with normalization of bone mass. It is not known whether the bone loss in hyperprolactinemic subjects represents a failure to achieve peak bone mass or is due to accelerated bone loss. Despite low bone density hyperprolactinemic subjects do not demonstrate increased fractures. The association between prolactin, weight gain and obesity suggests that prolactin may also be a modulator of body composition and body weight. It is not known whether hyperprolactinemia associated weight gain is due to stimulation of lipogenesis or due to disruption of central nervous system dopaminergic tone. Hyperprolactinemia is also associated with insulin resistance and endothelial dysfunction which may improve after normalization of prolactin. The clinical significance of these findings and the precise role of prolactin in regulation of weight and metabolism remain to be elucidated.

Prolactin and breast cancer etiology: an epidemiologic perspective

A number of epidemiologic studies of prolactin and breast cancer etiology have recently become available. Retrospective case-control studies have suggested a modest positive or null relationship between circulating prolactin concentrations and risk of breast cancer. However these studies are limited by small sample sizes and the collection of blood after case diagnosis. Several large prospective studies, in which blood was collected prior to diagnosis, have observed modest positive associations between prolactin and risk. In a pooled analysis of approximately 80% of the world's prospective data, the relative risk (RR) comparing women in the top vs bottom quartile of prolactin levels was 1.3 (95% confidence interval (CI): 1.1, 1.6, p-trend = 0.002). The results were similar for premenopausal and postmenopausal women. Most notably, high prolactin levels were associated with a 60% increased risk of estrogen receptor (ER) positive tumors, but not with ER negative tumors. Limited genetic data suggest a role of polymorphisms in the prolactin and prolactin receptor genes in risk of breast cancer. Studies of survival have suggested that high pretreatment prolactin levels were associated with treatment failure, earlier recurrence, and worse overall survival. Parity and certain medications are the only confirmed factors associated with prolactin levels in women. Overall, epidemiologic data suggest that prolactin is involved in breast cancer etiology. Further research to better elucidate these associations and their underlying mechanisms is warranted.

Prolactin does not cause breast cancer and may prevent it or be therapeutic in some conditions

The polypeptide hormone prolactin (PRL), ubiquitous and multifunctional in vertebrates, always interested biologists, was of restricted concern to clinicians and researched little compared to insulin and growth hormone. PRL in lactation initially aroused relatively little interest, but it rose when with ovarian steroids and chemical carcinogens, it was implicated in rodent mammary carcinoma. It declined when PRL suppression did not counter breast cancer. Meanwhile, long-known, estrogen-related cancers in the ovary and breast did not deter wide estrogen use for contraception and supplementation despite risk, and estrogen blockers and inhibitors have improved treatment and are on trial for prophylaxis, despite serious short and long term side-effects. Despite the great differences between steroid and polypeptide, research on PRL and breast cancer mirroring that on estrogens is now growing. This is mainly negative, much due to recent prospective research reporting minor rises in plasma levels as a basis, together with some recent laboratory research, for a hypothesis that PRL induces post-menopausal breast cancer. That view contradicts a reproductive biology that evolved to benefit women and offspring. Elevated PRL in pregnancy and probably that in lactation, reduce risk. Many exogenous chemical and physical PRL-stimulants also do not increase risk. It has not been shown that PRL increases risk of breast cancer and some older and recent cell and tissue data suggest it may be the key, two-sided, in human breast tissue homeostasis. Excessive disturbance of this is unlikely to originate in PRL itself. The natural biology of PRL, the reproductive woman's hormone par excellence, and research in various fields, suggest a positive potential in the PRL family for direct prevention and treatment of breast cancer, possibly greater than that in the estrogens. It is time to debate and research this.

Reproductive factors and family history of breast cancer in relation to plasma prolactin levels in premenopausal and postmenopausal women

Many reproductive factors are associated with breast cancer risk, potentially through a hormonal pathway. The peptide hormone prolactin is essential in mammary development and lactation and may be a link between risk factors and breast cancer. While higher prolactin levels are associated with increased breast cancer risk, few determinants of prolactin levels are known. We conducted a cross-sectional analysis among 1,089 premenopausal and 1,311 postmenopausal women within the Nurses' Health Study (NHS) and the NHS II to examine the associations of reproductive factors, benign breast disease and family history of breast cancer with plasma prolactin levels. Parous women had significantly lower prolactin levels than nulliparous women (parous vs. nulliparous multivariate-adjusted geometric means = 14.1 ng/mL vs. 16.6 ng/mL, p<0.001 for premenopausal and 9.1 vs. 10.1, p=0.04 for postmenopausal women), although levels did not decrease with increasing number of children for either premenopausal (p-trend = 0.23) or postmenopausal (p-trend = 0.07) parous women. Age at first birth was not associated with prolactin levels. The reduction in prolactin levels among parous premenopausal women appeared to attenuate with increasing time since first birth, but the trend was not statistically significant (p-trend = 0.12). Age at menarche, duration of lactation and benign breast disease were not associated with prolactin levels. Family history of breast cancer was associated with significantly higher prolactin levels when compared with no family history among premenopausal (15.9 ng/mL vs. 14.3 ng/mL, p=0.04) but not postmenopausal (p=0.73) women. In conclusion, the associations of parity and family history with breast cancer risk may be mediated, at least in part, by prolactin levels.

Weight gain with olanzapine: Drug, gender or age?

BACKGROUND

The introduction of atypical antipsychotics was a big step forward in the treatment of schizophrenia and other psychoses. Their limitations, however, became evident over time.

AIM

To study the causes of weight gain associated with the use of olanzapine-an atypical antipsychotic drug.

METHODS

Eighty patients fulfilling the ICD-10 criteria for schizophrenia, predominantly with negative symptoms, were included in this study to evaluate weight gain as an adverse effect of treatment with olanzapine in relation to age, gender, dose and body mass index (BMI). Sociodemographic data and baseline weight along with height (to calculate the BMI) were recorded before the initiation of treatment. The patients were administered a flexible dose of olanzapine (5-15 mg) as monotherapy. Pregnant patients, smokers and those with endocrine disorders, cardiac problems and organic brain dysfunction were excluded from the study. The increase in weight as a neuroleptic side-effect of olanzapine was recorded and analysed in relation to age, gender, dose and BMI.

RESULTS

Of the patients receiving olanzapine, 66.6% had a weight gain of 1-5 kg over a period of 4 weeks. The weight gain was not related to the dose of the drug or BMI. The interesting finding was that the increase in weight was significantly related to age >/=40 years and female sex, indicating that women >/=40 years of age are more prone to gain weight with olanzapine therapy in comparison with women <40 years and men of any age group.

CONCLUSION

The potential for weight gain associated with the use of atypical antipsychotics to cause long-term complications will need further study. Clinicians are encouraged to monitor weight, plasma glucose and leptin levels, and lipid parameters in patients receiving olanzapine.

Reversible weight gain and prolactin levels--long-term follow-up in childhood

In adult patients weight gain is a frequent complaint of hyperprolactinaemia and it has been associated with a high prevalence of obesity. Normalization of prolactin (PRL) levels result in weight loss. The nature of this link is poorly defined. In this report we describe a 14 year-old female with primary amenorrhea and persistent progressive weight gain. The patient's height, weight and BMI were 152 cm, 70 kg, and 30.3 kg/m2, respectively. Basal hormonal investigation showed normal free thyroxin, TSH, IGF-I, cortisol and ACTH values. Serum PRL level was very high (16,278 mIU/l; normal range 63-426 mIU/l). Magnetic resonance imaging scan showed the presence of a pituitary microadenoma. Treatment with the non-selective dopamine agonist pergolide caused a significant reduction of serum PRL concentration with a remarkable decrease of body weight. During follow-up, repeat MRI scan revealed disappearance of the microadenoma. The reduction of the daily dose of pergolide was associated with an increase of serum PRL with significant weight gain. A further reduction of body weight was subsequently observed with an increase of pergolide dosage. Serum PRL measurement may be useful as part of the endocrine work-up of obese children with a history of unexplained recent weight gain, especially if associated with pituitary-gonadal axis dysfunction. The relationship between PRL secretion and weight change needs to be examined in prospective larger studies.

Selective exposure reporting and Medline indexing limited the search sensitivity for observational studies of the adverse effects of oral contraceptives

OBJECTIVE

To explore development of possible approaches leading to a sensitive and precise Medline search to identify observational studies of the association between oral contraceptives and breast cancer, an adverse event.

STUDY DESIGN AND SETTING

We compared the results of a series of Medline searches to a gold standard comprising 58 reports from a 1996 systematic review examining the relationship between oral contraceptives and the development of breast cancer. Sensitivity (the proportion of gold standard publications identified) and precision (the proportion of retrieved publications that were included in the gold standard) were calculated for each Medline search.

RESULTS

We identified all 58 articles when the search was not limited by terms related to oral contraceptives, but precision was less than 1% (58 of 6,120). Indexing was problematic when oral contraceptives or hormones were not mentioned in the title or abstract (n = 8) or full text (n = 2).

CONCLUSION

Search strategies identifying all relevant studies were possible but arguably impractical; additional research is needed to generalize our findings. Authors and editors should ensure that all interventions and outcomes examined are reported and indexers should make sure they are indexed. Central registration of observational studies and all variables they examined should be considered to assure identification of studies examining adverse events associated with health interventions.

No association between serum levels of insulin-like growth factor-I, vascular endothelial growth factor, prolactin and clinicopathological characteristics of breast carcinoma after surgery

BACKGROUND

Angiogenesis is essential for tumour growth and metastasis. Vascular endothelial growth factor (VEGF) has been suggested as the major angio-genic factor in breast carcinoma. Both insulin-like growth factor-I (IGF-I) and prolactin are involved in the progression of breast cancer at least partly by stimulating angiogenesis.

AIM

The aim of the present study was to investigate the association between serum IGF-I, VEGF and prolactin levels and clinicopathological characteristics of breast carcinoma.

METHODS

Serum IGF-I, VEGF and prolactin levels were measured in breast cancer patients and controls and these levels were compared with well-known clinicopathological characteristics of breast carcinoma, including tumour size, axillary lymph node and oestrogen/progesterone receptor status, tumour grade and disease stage.

RESULTS

Serum prolactin, VEGF and IGF-I levels were found to be similar in breast cancer patients and control subjects (P > 0.05). When the patients were divided into groups according to their tumour size, axillary lymph node status, tumour grade, oestrogen/progesterone receptor status and disease stage, no significant differences in serum prolactin, VEGF and IGF-I levels were found among the groups (P > 0.05).

CONCLUSIONS

The present study failed to demonstrate an association between serum levels of VEGF, IGF-I and prolactin and well-known clinicopathological characteristics of breast carcinoma.

Variability of breast cancer risk in observational studies of hormone replacement therapy: a meta-regression analysis

OBJECTIVES

A re-analysis of data from 51 epidemiological studies reported a significant 14% increase in the risk of breast cancer associated with the use of hormone replacement therapy (HRT). Unlike randomized trials, these observational studies varied in design and methods. This study was conducted to explore the impact of study design factors on the rate ratio.

METHODS

We performed a meta-regression analysis of 39 epidemiological studies of HRT and breast cancer. The rate ratio of breast cancer associated with ever use of HRT was evaluated in relation to study design, study period, country, primary study objective, method of exposure measurement, age control, adjustment factors related to reproduction and menopause, and the presence of breast cancer surveillance. We used stepwise multiple regression analysis, weighted by the inverse of the variance of the logarithm of the rate ratio, to estimate ratios of rate ratios for these factors.

RESULTS

Exposure measured by personal interview and/or medical record review was associated with a 14% lower rate ratio estimate as compared with telephone interview or self-administered questionnaire (P = 0.018). Among studies that did not adjust for age at menopause, the rate ratio was 12% lower if the primary objective was HRT effect than not (P = 0.016), while it was 43% higher among studies that adjusted for age at menopause (P = 0.042). An index that included as six desirable design features, breast cancer surveillance, matching of controls, more reliable exposure information, adjustment for age at menopause and reproductive risk factors, and as primary objective the effect of HRT suggests that studies with none of these properties would lead to a rate ratio estimate of 1.14 (95% CI: 1.00-1.29) while studies with all six properties would produce a rate ratio of 0.98 (95% CI: 0.83-1.15).

CONCLUSIONS

Design factors of epidemiological studies could be an alternative explanation for the reported 14% increase in the risk of breast cancer associated with the use of HRT.

Serotonergic and histaminergic mechanisms involved in intralipid drinking?

Some newer antipsychotic agents are associated with weight gain in humans and a hyperphagic response to intralipid solutions in rodents. To examine the possible contribution of serotonin (5-HT) and histamine (H) receptor blockade in antipsychotic-associated hyperphagia, rats were trained to drink a palatable, high-calorie fat emulsion (10% intralipid) during 30-min sessions and were tested following pretreatment with mepyramine (H1 receptor antagonist), metergoline (5-HT(1/2) receptor antagonist), cyproheptadine (H1 and 5-HT(2A/2B/2C) and muscarinic receptor antagonist), SB 242084 (5-HT2C receptor antagonist) and an SB 242084-mepyramine combination. Total intake and ingestive behaviour microstructure were measured. Mepyramine (10 mg/kg) reduced intake, as did metergoline (3.0 mg/kg). Cyproheptadine (0.1-1.0 mg/kg) increased intake and microstructural analysis suggests that this was due to increased numbers of clusters of licking. SB 242084 (3 mg/kg) reduced intake, either when administered alone, or in combination with mepyramine (1 mg/kg). In conclusion, simple antagonism of either H1 (mepyramine) or 5-HT(1/2) receptors (metergoline) alone was not sufficient to increase intake. Furthermore, combined blockade of H1 and 5-HT2C receptors (SB 242084 and mepyramine) was also insufficient to produce hyperphagia. Conversely, simultaneous blockade of H1, 5-HT(2A/2C) and muscarinic receptors (cyproheptadine) led to a substantial hyperphagia and pattern of ingestive behaviour that was similar to that previously observed with some newer antipsychotic agents.

Antipsychotic metabolic effects: weight gain, diabetes mellitus, and lipid abnormalities

OBJECTIVE

To review published and nonpublished literature describing changes in weight, glucose homeostasis, and lipid milieu with antipsychotics.

METHODS

A Medline search was completed using the words weight gain, diabetes mellitus, cholesterol, triglycerides, risperidone, clozapine, olanzapine, quetiapine, ziprasidone, predictors, prolactin, obesity, and conventional antipsychotics. Publications, including original articles, review articles, letters to the editor, abstracts or posters presented at professional meetings in the last 4 years, and references from published articles, were collected. Manufacturers, including Eli Lilly Canada Inc, JanssenOrtho Inc, Pfizer Canada Inc, AstraZeneca Inc, and Novartis Pharmaceuticals, were contacted to retrieve additional medical information.

RESULTS

The topic of antipsychotic-induced weight gain is understudied, and there are relatively few well-controlled studies. Weight gain as a side effect has been described with both conventional and atypical antipsychotics. Moreover, some atypical antipsychotics are associated with de novo diabetes mellitus and increased serum triglyceride levels. Predictors of weight gain may be age, baseline body mass index, appetite stimulation, previous antipsychotic exposure, and antipsychotic treatment duration.

CONCLUSION

Significant weight gain is reported with the existing atypical antipsychotics. The weight gain described is highly distressing to patients, may reduce treatment adherence, and may increase the relative risk for diabetes mellitus and hypertriglyceridemia. Physicians employing these agents should routinely monitor weight, fasting blood glucose, and lipid profiles.

Stimulation of prolactin secretion by chronic, but not acute, administration of leptin in the rat

Leptin, the product of obese (ob) gene, has been reported to affect the secretion of all six anterior pituitary hormones, but data are especially scarce regarding the interplay between leptin and prolactin (PRL). Thus, in this study we examined and compared in vivo the effects of acute and chronic administrations of recombinant mouse leptin on PRL secretion in male rats. Normally-fed and 3-day-fasted rats received an intraperitoneal bolus injection of leptin [1.0 mg/kg body weight (BW)] or vehicle only. The leptin treatment was without effect on plasma PRL levels up to 5 h postadministration. Food deprivation for 3 days significantly decreased both PRL and leptin levels. This decrease in plasma PRL was prevented by a 3-day constant infusion of 75 microg/kg BW/day of leptin, which maintained plasma leptin levels similar to those of normally-fed rats. The administration of three times the higher dose of leptin (225 microg/kg BW/day) to fasted rats led to further increases in both PRL and leptin in the plasma. Thus, a dose-dependent stimulatory effect of chronic leptin treatment on PRL secretion was indicated. This study demonstrates that chronic, but not acute, administration of leptin stimulates PRL secretion in the rat.

Endocrine effects of lithium carbonate in healthy premenopausal women: relationship with body weight regulation

The mechanisms involved in Li-induced weight gain remain unclear. The higher frequency of obesity in women than in men under Li treatment, suggests a role for reproductive hormones. The serum levels of the following hormones were evaluated in healthy young women at diverse stages of a control menstrual cycle, and during Li carbonate (900 mg/day) or placebo administration: prolactin, luteinizing hormone, follicle-stimulating hormone, 17-1 estradiol, progesterone, thyroxine, thyrotropin, cortisol, dehidroepiandrosterone sulfate, free testosterone, leptin and an oral glucose tolerance test, in order to measure the areas under the glucose and insulin curve. The body weight was assessed the day before and the last day of treatment. The Li serum levels 15 hours after the last dose were 0.31 +/- 0.1 mEq/L. No significant changes in body weight and in the normal fluctuations of the reproductive hormones along the menstrual cycle were observed during Li administration. An increase in the serum levels of thyrotropic hormone ( p = 0.0001) was the only significant effect of Li, which may predispose to excessive weight gain after prolonged administration of the cation. The remarkable lack of effects of Li on these hormones, question the pertinence of studies conducted in healthy volunteers for the comprehension of the obesity observed in psychiatric patients who may be particularly prone to gain weight under prolonged treatment with high dose of Li.

Body weight gain induced by antipsychotic drugs: mechanisms and management

Long-term administration of typical and atypical antipsychotic drugs (AP) induces excessive weight gain which afflicts up to 50% of patients, impairs health and interferes with treatment compliance. Basic and clinical research has shown that AP may affect body weight through diverse mechanisms. Increased appetite is probably related to the interaction of AP with neuronal receptors to dopamine, serotonin and histamine. Additional metabolic-endocrine disruption of weight regulation may be related to the effects of AP-induced hyperprolactinaemia on gonadal-adrenal steroids and insulin sensitivity. In humans, programmed physical activity, dietary restriction, anorectic agents, and drugs that counteract hyperprolactinaemia have been shown to be successful in a limited number of studies. Two novel strategies could expand the available therapeutic options. First, in preclinical experiments in female rats the estradiol antagonist/agonist drug tamoxifen or estradiol itself have been shown to completely prevent the obesity provoked by the AP sulpiride, and to induce an endocrine-metabolic milieu that seems to counteract AP-induced obesity. Secondly, it has also been shown that oral antihyperglycaemic agents such as metformin may decrease body weight and counteract insulin resistance and hyperinsulinaemia which is correlated with several metabolic abnormalities in obese subjects. Lastly, estradiol replacement, tamoxifen and/or antihyperglycaemic agents are not devoid of significant side-effects, and these drugs have not been tested in obese psychiatric patients. Therefore, further research is needed before their clinical use may be recommended.

Glucose tolerance and serum insulin levels in an animal model of obesity induced by the antipsychotic drug, sulpiride

To assess the role of insulin in the development of obesity induced by antipsychotic drugs, a glucose tolerance test was conducted in 40 female rats during the peak of sulpiride-induced weight gain and in 40 vehicle-treated animals. The glucose area under the curve did not differ between the groups (P = 0.24), however, the area under the insulin curve was significantly decreased by sulpiride (55.2 +/- 2.8 versus 115.6 +/- 18.9, P = 0.007). The results suggest that insulin resistance and hyperinsulinaemia are not involved in the excessive weight gain observed in this animal model of drug-induced obesity. Alternatively, the insulin-dampened response observed in the sulpiride-treated rats may be related to increased insulin sensitivity, which may promote weight gain as proposed by Ravussin (1995).

Increased body weight associated with prolactin secreting pituitary adenomas: weight loss with normalization of prolactin levels

OBJECTIVE

Hyperprolactinaemia in humans may be associated with a high prevalence of obesity but the nature of this link is poorly defined. The aim of this study was to establish the relationship between hyperprolactinaemia and body weight in patients with prolactin-secreting pituitary tumours.

DESIGN

We conducted a retrospective study of prolactinoma patients treated at the Endocrine Institute of the Tel Aviv Medical Center, Israel, during the period 1989-1996. Patients with clinically non-functioning pituitary macroadenomas (NFA) served as the control group. Data on demographic parameters, body weight before and during treatment, clinical presentation including history of weight fluctuations, tumour size as measured by computed tomography or magnetic resonance imaging, modalities and response to treatment, and pituitary function before and during treatment were recorded from medical files.

PATIENTS

Forty-two patients with prolactinomas (PR) and 36 patients with clinically non-functioning macroadenomas (NFA) comprised the study population.

RESULTS

Mean weight was 93 +/- 3.4 kg and 78 +/- 2.7 kg in male patients with PR and NFA respectively (P = 0.0007). Recent weight gain (8 to 22 kg) was a presenting symptom in 13 PR patients, whereas only one NFA patient had this clinical presentation (P = 0.001). Seventeen PR patients lost weight (mean change -8.3 +/- 1.5 kg, range -2-28 kg), during prolactin lowering therapy, 11 of whom had entirely normalized prolactin levels. Fourteen of the 18 patients who did not lose weight still had elevated prolactin levels (P = 0.01). Weight loss in patients with PR could not be attributed to altered pituitary function nor to compression of the third ventricle. In contrast to PR, no significant weight loss was observed in NFA patients.

CONCLUSION

Weight gain and elevated body weight are frequently associated with prolactinomas regardless of a mass effect on the hypothalamus or pituitary function. In this series, weight loss was recorded in 70% of prolactinomas patients and in 90% of male patients who normalized their prolactin levels. We propose the inclusion of hyperprolactinaemia in the differential diagnosis of endocrine obesity and weight gain.

Breast cancer and hormone replacement therapy: collaborative reanalysis of data from 51 epidemiological studies of 52,705 women with breast cancer and 108,411 women without breast cancer. Collaborative Group on Hormonal Factors in Breast Cancer

BACKGROUND

The Collaborative Group on Hormonal Factors in Breast Cancer has brought together and reanalysed about 90% of the worldwide epidemiological evidence on the relation between risk of breast cancer and use of hormone replacement therapy (HRT).

METHODS

Individual data on 52,705 women with breast cancer and 108,411 women without breast cancer from 51 studies in 21 countries were collected, checked, and analysed centrally. The main analyses are based on 53,865 postmenopausal women with a known age at menopause, of whom 17,830 (33%) had used HRT at some time. The median age at first use was 48 years, and 34% of ever-users had used HRT for 5 years or longer. Estimates of the relative risk of breast cancer associated with the use of HRT were obtained after stratification of all analyses by study, age at diagnosis, time since menopause, body-mass index, parity, and the age a woman was when her first child was born.

FINDINGS

Among current users of HRT or those who ceased use 1-4 years previously, the relative risk of having breast cancer diagnosed increased by a factor of 1.023 (95% CI 1.011-1.036; 2p=0.0002) for each year of use; the relative risk was 1.35 (1.21-1.49; 2p=0.00001) for women who had used HRT for 5 years or longer (average duration of use in this group 11 years). This increase is comparable with the effect on breast cancer of delaying menopause, since among never-users of HRT the relative risk of breast cancer increases by a factor of 1.028 (95% CI 1.021-1.034) for each year older at menopause. 5 or more years after cessation of HRT use, there was no significant excess of breast cancer overall or in relation to duration of use. These main findings did not vary between individual studies. Of the many factors examined that might affect the relation between breast cancer risk and use of HRT, only a woman's weight and body-mass index had a material effect: the increase in the relative risk of breast cancer associated with long durations of use in current and recent users was greater for women of lower than of higher weight or body-mass index. There was no marked variation in the results according to hormonal type or dose but little information was available about long durations of use of any specific preparation. Cancers diagnosed in women who had ever used HRT tended to be less advanced clinically than those diagnosed in never-users. In North America and Europe the cumulative incidence of breast cancer between the ages of 50 and 70 in never-users of HRT is about 45 per 1000 women. The cumulative excess numbers of breast cancers diagnosed between these ages per 1000 women who began use of HRT at age 50 and used it for 5, 10, and 15 years, respectively, are estimated to be 2 (95% CI 1-3), 6 (3-9), and 12 (5-20). Whether HRT affects mortality from breast cancer is not known.

INTERPRETATION

The risk of having breast cancer diagnosed is increased in women using HRT and increases with increasing duration of use. This effect is reduced after cessation of use of HRT and has largely, if not wholly, disappeared after about 5 years. These findings should be considered in the context of the benefits and other risks associated with the use of HRT.

Breast cancer and hormonal contraceptives: collaborative reanalysis of individual data on 53 297 women with breast cancer and 100 239 women without breast cancer from 54 epidemiological studies

BACKGROUND The Collaborative Group on Hormonal Factors in Breast Cancer has brought together and reanalysed the worldwide epidemiological evidence on the relation between breast cancer risk and use of hormonal contraceptives. METHODS Individual data on 53 297 women with breast cancer and 100 239 women without breast cancer from 54 studies conducted in 25 countries were collected, checked, and analysed centrally. Estimates of the relative risk for breast cancer were obtained by a modification of the Mantel-Haenszel method. All analyses were stratified by study, age at diagnosis, parity, and, where appropriate, the age a woman was when her first child was born, and the age she was when her risk of conception ceased. FINDINGS The results provide strong evidence for two main conclusions. First, while women are taking combined oral contraceptives and in the 10 years after stopping there is a small increase in the relative risk of having breast cancer diagnosed (relative risk [95 percent CI] in current users 1.24 [1.15-1.33], 2p<0.00001; 1-4 years after stopping 1.16 [1.08-1.23], 2p=0.00001; 5-9 years after stopping 1.07 [1.02-1.13], 2p=0.009). Second, there is no significant excess risk of having breast cancer diagnosed 10 or more years after stopping use (relative risk 1.01 [0.96-1.05], NS). The cancers diagnosed in women who had used combined oral contraceptives were less advanced clinically than those diagnosed in women who had never used these contraceptives for ever-users compared with never-users, the relative risk for tumours that had spread beyond the breast compared with localised tumours was 0.88 (0.81-0.95; 2p=0.002). There was no pronounced variation in the results for recency of use between women with different background risks of breast cancer, including women from different countries and ethnic groups, women with different reproductive histories, and those with or without a family history of breast cancer. The studies included in this collaboration represent about 90 percent of the epidemiological information on the topic, and what is known about the other studies suggests that their omission has not materially affected the main conclusions. Other features of hormonal contraceptive use such as duration of use, age at first use, and the dose and type of hormone within the contraceptives had little additional effect on breast cancer risk, once recency of use had been taken into account. Women who began use before age 20 had higher relative risks of having breast cancer diagnosed while they were using combined oral contraceptives and in the 5 years after stopping than women who began use at older ages, but the higher relative risks apply at ages when breast cancer is rare and, for a given duration of use, earlier use does not result in more cancers being diagnosed than use beginning at older ages. Because breast cancer incidence rises steeply with age, the estimated excess number of cancers diagnosed in the period between starting use and 10 years after stopping increases with age at last use: for example, among 10 000 women from Europe or North America who used oral contraceptives from age 16 to 19, from age 20 to 24, and from age 25 to 29, respectively, the estimated excess number of cancers diagnosed up to 10 years after stopping use is 0.5 (95 percent CI 0.3-0.7), 1.5 (0.7-2.3), and 4.7 (2.7-6.7). Up to 20 years after cessation of use the difference between ever-users and never-users is not so much in the total number of cancers diagnosed, but in their clinical presentation, with the breast cancers diagnosed in ever-users being less advanced clinically than those diagnosed in never-users. The relation observed between breast cancer risk and hormone exposure is unusual, and it is not possible to infer from these data whether it is due to an earlier diagnosis of breast cancer in ever-users, the biological effects of hormonal contraceptives, or a combination of reasons...

Serum prolactin levels and their relationship to survival in women with operable breast cancer

The prognostic value of serum prolactin levels was assessed in a sequential series of 739 patients who were initially treated at Guy's Hospital, London, between 1975 and 1980. Prolactin was measured in 472 patients 1 day before (Hpr1) and in 457 patients 10 days after (Hpr2) mastectomy. Follow-up of the patients was up to August 1992 giving 6139 women-years with a median follow-up time of 11.5 years (13.7 for patients still living and 5.1 for those dead). The association between the three prolactin variables and reproductive and clinical factors was examined before assessing the prognostic value of prolactin levels in terms of overall, disease-specific and disease-free survival. Multivariate survival models were used in order to adjust for the effect of other prognostic variables. These were found to be: tumour size, degree of nodal involvement, tumour grade and age at diagnosis. The results showed that high Hpr2 or high postoperative increase in prolactin (i.e. Hpr2-Hpr1) were significantly related to shorter disease-specific survival (p = 0.04 and 0.01, respectively) in postmenopausal women. In addition there was some indication, which did not attain formal significance, for this association to occur for disease-free survival. Thus the rise in blood prolactin levels after surgery may be a weak indicator of poor prognosis of breast cancer in postmenopausal women.

Endocrine and psychological evaluation of women with recent weight gain

A group of 13 consecutive regularly menstruating women who gained at least 5 kg the previous year (Group I) was compared to a control group of similar age, parity, and social class (Group II). The two groups were similar in estimated and observed food intakes; pre- and postprandial gastrin levels; hourly 24-h profiles of cortisol and insulin; urinary cortisol and 17-hydroxycorticosteroids. Group I had higher serum prolactin concentrations at all times than Group II (mean values 14.60 micrograms/l vs. 8.84 micrograms/l; p = .0121). Galactorrhea was observed in 5 women from Group I and in none of the women from Group II (p < .05). Group I also differed from Group II in a higher incidence of meaningful life-events the year preceding the study, higher prevalence of sexual dysfunction (9/13 vs. 4/13; p < .01) and higher indexes (p < .05) of several parameters in the MMPI and SCL 90. Median serum cortisol and prolactin concentrations were negatively correlated, both in Group I (R = -.669; p = .012) and in the whole sample (R = -.453; p = .0298). It is suggested that the rapid weight gain is part of a neuroendocrine response to environmental stimuli also characterized by hyperprolactinemia. The significant negative correlation between serum prolactin and cortisol indicates that this response differs from, and is possibly an alternative to, the sympathoadrenal "stress" response.

Hormonal and clinic evaluation of patients with moderate body hair growth

Plasma prolactin (PRL), gonadotropins (FSH, LH), estradiol-17 beta (E2), progesterone (P), total testosterone (T), sex steroid binding protein (SBP), T/SBP index, cortisol (F), 17-OH-progesterone (17OH-P), dehydroepiandrosterone sulphate (DHEA-S) and androstenedione (A), were measured in 50 fertile non-obese women presenting with moderate body hair growth and in 30 matched controls. DHEA-S and PRL were significantly higher (P < 0.002, P < 0.001, respectively) and SBP was lower (P < 0.001) in patients than in controls. Regression analyses showed that PRL levels were independent of the other parameters, while a negative correlation was found between DHEA-S and SBP values. Since the decision to treat a woman with mild body hair growth is usually a clinical one, PRL behaviour has to be taken into account before deciding the type of treatment. Clinical improvement was observed in subjects treated with ethynylestradiol plus desogestrel or plus cyproterone acetate, so as to produce an increase in SBP rather than a decrease in DHEA-S.

Plasma prolactin in relation to menstrual cycle phase, oral contraceptive use, arousal time and smoking habits

The study was designed to investigate if modern low dosage combined oral contraceptives were associated with changes in plasma prolactin levels in healthy nulliparous women aged 19-25. Plasma prolactin was not significantly correlated to oral contraceptive use, nor to smoking habits. Plasma prolactin was, however, significantly negatively correlated to time since awakening. A significant two-way interaction on prolactin was also seen between smoking and present oral contraceptive use. In our material the mean values of plasma prolactin were higher in the follicular phase than in the luteal phase, although not significantly.

Human breast cancer: concerted role of diet, prolactin and adrenal C19-delta 5-steroids in tumorigenesis

The low incidence of breast cancer in Japan disappears within 2 generations in migrant Japanese in the USA. This is of fundamental importance if we are to understand, and perhaps reverse, the high rate seen in Western countries. Diet is the most likely factor involved, and a review of the topic of diet, body mass index, and gain in adult body mass, supports a relationship between these factors and breast-cancer risk in post-menopausal, but not pre-menopausal, women. A direct link between nutritional factors and secretion of the hormones prolactin and dehydroepiandrosterone sulfate is proposed. An estrogen 5-androstene-3 beta, 17 beta-diol is formed peripherally from the latter steroid, and in Western women attains a blood concentration at which it is biologically active. Thus diet/fat provides factors, viz., fatty acids, prolactin and estrogen, which in concerted fashion provide a milieu conducive to mammary tumorigenesis.

Epidemiological and biochemical support for a theory on the cause and prevention of breast cancer

Damage to the breast epithelium by chemical carcinogens as products of oxygen free radical release can lead to fibroblast proliferation, hyperplasia of epithelium, cellular atypia and breast cancer. Chemical carcinogens may accumulate in breast fluid in the non-lactating breast consequent to superoxide free radical production which occurs via the adenosine triphosphate (ATP) hypoxanthine pathway. This pathway is initiated by hypoxia of local tissue. Under hypoxic conditions ATP is broken down to form hypoxanthine. Hypoxanthine itself is broken down to produce xanthine and then uric acid. This results in the production of superoxide free radicals, the products of which are carcinogenic. The development of localized hypoxia, which is central to this hypothesis, is caused by acinal gland distention from fluid secreted by raised prolactin levels in the absence of oxytocin. Stimulation of the nipple in a non-lactating breast may raise plasma oxytocin and lower plasma prolactin levels. Contraction of the myoepithelial cells of the breast under the influence of oxytocin would relieve distention of the acinal glands and thus reduce hypoxia and the generation of lipid peroxidoses as products of free radical damage. The epidemiology of breast fibrosis and cancer support the notion that lack of nipple stimulation over time may be a significant variable. A review of this literature linked with current biochemical work on fibrosis and carcinogenesis suggest that draining the breasts of the products of superoxide free-radical release by the encouragement of regular nipple erections may prevent such breast disease.

Serum hormone levels in British and rural Chinese females

The comparison of blood levels of oestradiol, testosterone, prolactin, and sex-hormone binding globulin (SHBG) was made of 3250 rural Chinese and 300 British women, aged 35 to 64. To reduce the number of assays performed the blood samples were combined so as to form 390 and 30 pools, respectively. The Chinese had significantly less oestradiol and testosterone. Prolactin levels were similar in both races. SHBG was significantly lower in postmenopausal British women. In the Chinese women, testosterone was positively and prolactin negatively correlated with breast cancer mortality.

Sex hormones in women in rural China and in Britain

Plasma concentrations of certain hormones linked to breast cancer risk were measured in age-pooled samples from 3,250 rural Chinese women in 65 counties, and 300 British women, all aged 35-64. In age-groups 35-44, 45-54 and 55-64 respectively, mean oestradiol concentrations were 36% (P = 0.043), 90% (P less than 0.001) and 171% (P = 0.001) higher in the British than in the Chinese women, and mean testosterone concentrations were 48% (P less than 0.001), 68% (P less than 0.001) and 53% (P = 0.001) higher in the British than in the Chinese women. The difference in testosterone concentrations between the two countries appeared to be due largely to the lower average body weight in the Chinese women. Sex hormone binding globulin did not differ significantly between the two countries in age groups 35-44 and 45-54, but was 15% (P = 0.002) lower in the British than in the Chinese women at ages 55-64. Prolactin concentrations did not differ significantly between the two countries in any age group.

Plasma prolactin as an indicator of disease progression in advanced breast cancer

Serial plasma prolactin levels were measured in 144 breast cancer patients (premenopausal [PR-M], N = 64; postmenopausal [PO-M], N = 80) and compared with respective controls. Patients with breast cancer were grouped into those who (1) developed distant metastasis, (2) developed local recurrence, (3) stable disease, and (4) responded to the various therapeutic modalities at the end of 2 years. The authors' analysis showed excellent correlation between serial plasma prolactin changes and the response to therapy or progression of disease in patients with advanced breast carcinoma.

Serum bioactive lactogenic hormone levels in women with familial breast cancer and their relatives

Serum levels of bioactive lactogenic hormone (BLH), immunoreactive prolactin and growth hormone (ir-PRL and ir-GH) were measured in a group of familial breast cancer patients and their first degree female relatives and compared to those found in normal healthy women. The ratio of BLH to the sum of ir-PRL and ir-GH was slightly but significantly decreased in the familial breast cancer group (P = 0.018 by the Mann-Whitney U test) although there were no significant differences in the levels of BLH, ir-PRL and ir-GH between the two groups. No differences in the levels of the lactogenic hormones could be detected when the pre-menopausal women were considered separately or when 20 women from the familial group were compared to normal controls matched for age, parity, weight and menopausal status. The levels of BLH were highly correlated with the sum of ir-PRL and ir-GH in both the familial breast cancer group and the controls (P less than 0.001 for both groups by Spearman's rank correlation test). These findings are not indicative of the presence of an additional species of bioactive, but not immunoreactive, lactogen in the sera of women with or at high risk of breast cancer. However, the presence of different, but equipotent, forms of lactogen cannot be excluded in these women.

A prospective study of the independent effects of parity and age at first birth on breast cancer incidence in England and Wales

The independent effects of parity and age at first birth on breast cancer incidence are investigated in a 1% sample of women aged 16 to 59 from the 1971 Census of England and Wales. Over the period 1971-81, 1,003 breast cancer cases occurred in the cohort of 113,263 women who were either married, widowed or divorced at the time of Census. Age at first birth was positively related to breast cancer risk, women giving birth to their first child after 35 years being at greater risk than nulliparous women. This effect remained, after adjustment for number of live-born children. Breast cancer risk showed a statistically significant decline with increasing parity even after adjustment for age at first birth. These results are consistent with other published evidence which suggests that other births subsequent to the first have an independent effect on breast cancer risk.

The permanent effect of reproductive events on blood prolactin levels and its relation to breast cancer risk: a population study of postmenopausal women

In each of two population-based studies conducted on the Island of Guernsey between 1967-1976 and 1977-1984, respectively, single specimens of blood were taken from over 5000 normal women. From these two studies there were 1173 and 946 postmenopausal women in whom blood prolactin was determined and multivariate analysis was used to establish the association between blood prolactin concentration and possible determinants of risk of breast cancer. Since prolactin levels were log-normally distributed these analyses were done on log-transformed data. The age at menarche or menopause, age at first or last childbirth, length of reproductive life (i.e. time from menarche to menopause) or post-menopausal life (i.e. time from menopause to time of blood sampling), contraceptive use and history of breast cancer were not significantly associated with blood prolactin concentration. Of significance were age, parity, time of blood sampling and assay drift. Ponderosity (Quetelet's Index) was positively associated with prolactin concentration and this was significant using a one-tail criterion. Women with a mammographic pattern designated DY by Wolfe had significantly higher prolactin levels than those with N1 patterns. However, the main finding to emerge was that after standardizing for all the other variables increasing parity was related to a step-wise reduction in blood prolactin levels. Since this had occurred in women who had had their last child up to 35 years previously it implies this effect is permanent. It could therefore be that the protective effect on breast cancer risk of multiparity and early first pregnancy could be mediated by such a life-long reduction in blood prolactin levels.