Novel Actions of Estrogen Receptor-ß on Anxiety-Related Behaviors by Trent D. Lund, Tomislav Rovis, Wilson C. J. Chung and Robert J. Handa

ESTROGENS ARE WELL-ESTABLISHED regulators of mood in humans and animals. Its effects, however, are varied, with both anxiolytic and anxiogenic actions, depending on factors such as age and stage of the reproductive cycle. In women, reduced estrogen levels, particularly at the menopause, are associated with depression, sleep disturbance, irritability, anxiety, panic disorders, and cognitive dysfunction (1, 2, 3). Estrogen replacement therapy in postmenopausal women is consistently reported to improve mood, feelings of general well being, and learning as well as increase general activity levels (3, 4). In contrast, an anxiogenic role for estrogens is suggested by the significantly higher level of depression reported in women compared with men (5, 6, 7), a sex difference that emerges at the time of puberty (5, 6, 7). Furthermore, research by Schmidt et al. (8) identified that women with severe premenstrual dysphoria developed anxiety and other mood symptoms when treated with estradiol in combination with leuprolide, an agonist analog of GnRH.

Similar effects of estradiol on anxiety and mood have been reported in rodents. For example, elevated levels of estradiol achieved during rodent proestrus, or after exogenous hormone injections to ovariectomized (OVX) females, exert anxiolytic actions in the elevated plus maze (9, 10); consistently, when endogenous estrogens are removed, via OVX, behavioral indices of anxiety increase (10, 11, 12, 13, 15).

DRN- Dorsal Raphe Nucleus in Midbrain E2 receptors regulate 5HT synthesis

(4) http://www.ncbi.nlm.nih.gov/pubmed/15820717?dopt=Abstract
Biol Psychiatry. 2005 Apr 15;57(8):938-42.

Estrogen receptor-beta regulates tryptophan hydroxylase-1 expression in the murine midbrain raphe. Gundlah C, Alves SE, Clark JA, Pai LY, Schaeffer JM, Rohrer SP. Synaptic Pharmaceutical Corporation, Paramus.

BACKGROUND: Distinct expression patterns of estrogen receptor (ER)-alpha and ER-beta are displayed in the murine central nervous system. ER-beta is the predominant form of the receptor expressed in the murine midbrain dorsal raphe nucleus (DRN). Tryptophan hydroxylase (TPH) is abundantly expressed in the serotonergic neurons of the DRN and is regulated by estrogen in both the monkey and the guinea pig.

METHODS: In this study we used immunocytochemistry to show that ER-beta and TPH are colocalized in the serotonergic cells of the murine DRN. We utilized the ER-alpha and ER-beta gene deletion mouse models and in situ hybridization to demonstrate that ER-beta is responsible for regulating TPH1 mRNA expression.

RESULTS: Estrogen increased TPH1 mRNA expression in the DRN of wild type and ER-alpha knockout mice (alpha-ERKO) but not ER-beta knockouts (beta-ERKO).

CONCLUSIONS: These data indicate that ER-beta is responsible for mediating estrogen regulated TPH1 expression in the murine DRN.

(5) http://www.ncbi.nlm.nih.gov/pubmed/19559077
Neuroscience. 2009 Oct 6;163(2):705-18. Epub 2009 Jun 23.

Estrogen receptor beta regulates the expression of tryptophan-hydroxylase 2 mRNA within serotonergic neurons of the rat dorsal raphe nuclei.

Donner N, Handa RJ. Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80526, USA.

Dysfunctions of the brain 5-HT system are often associated with affective disorders, such as depression. The raphe nuclei target the limbic system and most forebrain areas and constitute the main source of 5-HT in the brain. All 5-HT neurons express tryptophan hydroxylase-2 (TPH2), the brain specific, rate-limiting enzyme for 5-HT synthesis. Estrogen receptor (ER) beta agonists have been shown to attenuate anxiety- and despair-like behaviors in rodent models. Therefore, we tested the hypothesis that ER beta may contribute to the regulation of gene expression in 5-HT neurons of the dorsal raphe nuclei (DRN) by examining the effects of systemic and local application of the selective ER beta agonist diarylpropionitrile (DPN) on tph2 mRNA expression.

Ovariectomized (OVX) female rats were injected s.c. with DPN or vehicle once daily for 8 days. In situ hybridization revealed that systemic DPN-treatment elevated basal tph2 mRNA expression in the caudal and mid-dorsal DRN. Behavioral testing of all animals in the open field (OF) and on the elevated plus maze (EPM) on days 6 and 7 of treatment confirmed the anxiolytic nature of ER beta activation.

Another cohort of female OVX rats was stereotaxically implanted bilaterally with hormone-containing wax pellets flanking the DRN. Pellets contained 17-beta-estradiol (E), DPN, or no hormone. Both DPN and E significantly enhanced tph2 mRNA expression in the mid-dorsal DRN. DPN also increased tph2 mRNA in the caudal DRN. DPN- and E-treated rats displayed a more active stress-coping behavior in the forced-swim test (FST). No behavioral differences were found in the OF or on the EPM.

These data indicate that ER beta acts at the level of the rat DRN to modulate tph2 mRNA expression and thereby influence 5-HT synthesis in DRN subregions. Our results also suggest that local activation of ER beta neurons in the DRN may be sufficient to decrease despair-like behavior, but not anxiolytic behaviors.

(6) http://www.albany.edu/~cafrye/papers/walfFrye06review.pdf
Neuropsychopharmacology (2006) 31, 1097–1111,  2006 Nature

Perspective - A Review and Update of Mechanisms of Estrogen in the Hippocampus and Amygdala for Anxiety and Depression Behavior by Alicia A Walf1 and Cheryl A Frye

Estrogen (E2) has many effects in the central nervous system, including effects on anxiety and depression behavior. This review will address effects of E2 on behaviors related to anxiety and depression in women and animal models and include recent findings from our laboratory related to this topic. E2’s antianxiety and antidepressant-like effects may depend upon many factors, including the regimen of
E2 utilized and interactions with the hypothalamic–pituitary–adrenal axis. Brain targets for E2’s effects on anxiety and depression include the hippocampus and amygdala.

Administration of E2, compared to vehicle, subcutaneously or to the hippocampus or amygdala of ovariectomized rats decreases anxiety and depressive behavior. Intracellular estrogen receptors (ERs) may be important for E2’s anxiolytic and antidepressant-like effects. Administration of an ER antagonist to the hippocampus, but not amygdala, increases anxiety and depression behavior of naturally receptive female rats.  Studies utilizing ER knockout mice or selective ER modulators suggest that
ER-mediated effects of E2 on anxiety and depressive behavior may require ERb.


Estradiol Treats Depressive Disorder- Clinical Studies 

Perimenopausal Mood Disorder and Depression

https://www.healthsystem.virginia.edu/
internet/neuroscience/BehavioralNeuroscience/soares-et-al.pdf

(7) http://www.ncbi.nlm.nih.gov/pubmed/11386980
Arch Gen Psychiatry. 2001 Jun;58(6):529-34.

Efficacy of estradiol for the treatment of depressive disorders in perimenopausal women: a double-blind, randomized, placebo-controlled trial. by Soares CN, Almeida OP, Joffe H, Cohen LS. Perinatal and Reproductive Psychiatry Clinical Research Program, Massachusetts General Hospital, Harvard Medical School, 15 Parkman St, WACC 812, Boston, MA

BACKGROUND: Results of previous studies suggest that estrogen improves somatic and mild depressive symptoms experienced by perimenopausal women. This study investigated the efficacy of 17beta-estradiol for the treatment of clinically significant depressive disorders in endocrinologically confirmed perimenopausal women.

METHODS: Perimenopausal women (aged 40-55 years, with irregular menstrual periods and serum concentrations of follicle-stimulating hormone >25 IU/L), meeting criteria for major depressive disorder, dysthymic disorder, or minor depressive disorder, according to DSM-IV, were randomized to receive transdermal patches of 17beta-estradiol (100 microgram) or placebo in a 12-week, double-blind, placebo-controlled study. A 4-week washout period followed the 12-week treatment phase. Outcome measures were the Montgomery-Asberg Depression Rating Scale and Blatt-Kupperman Menopausal Index scores.

RESULTS: Fifty women were enrolled in the study; 26 met DSM-IV criteria for major depressive disorder, 11 for dysthymic disorder, and 13 for minor depressive disorder. Remission of depression was observed in 17 (68%) women treated with 17beta-estradiol compared with 5 (20%) in the placebo group (P =.001). Subjects responded similarly to estradiol treatment, regardless of DSM-IV diagnosis. Patients treated with estradiol sustained antidepressant benefit of treatment after the 4-week washout period, although somatic complaints increased in frequency and intensity. Treatment was well tolerated and adverse events were rare in both groups.

CONCLUSION: Transdermal estradiol replacement is an effective treatment of depression for perimenopausal women.

Estrogen Treatment in Post Partum Depression in pts with low serum estrogen

(8) http://www.ncbi.nlm.nih.gov/pubmed/11411813
J Clin Psychiatry. 2001 May;62(5):332-6.

Estrogen deficiency in severe postpartum depression: successful treatment with sublingual physiologic 17beta-estradiol: a preliminary study.by Ahokas A, Kaukoranta J, Wahlbeck K, Aito M. Psychiatric Research Unit, Mehilainen Clinic, University of Helsinki, Finland.  

BACKGROUND: The postpartum period is a time when women are vulnerable to depressive disorders, which can be severe and have long-lasting adverse sequelae. In spite of multiple contacts with health care providers, women with postpartum depression often remain unrecognized and untreated. To evaluate the association between estradiol and postpartum depression, we measured serum estradiol concentration and performed an open-label study of physiologic 17beta-estradiol.

METHOD: Twenty-three women fulfilling ICD-10 criteria for major depression with postpartum onset were consecutively recruited from a psychiatric emergency unit. Serum estradiol concentrations were measured at baseline and weekly during sublingual 17beta-estradiol treatment for 8 weeks. The treatment effect was assessed using a clinician-rated depression symptom scale, the Montgomery-Asberg Depression Rating Scale (MADRS).

RESULTS: At baseline, all patients were severely depressed (mean MADRS total score = 40.7; range, 35-45) and had a low serum estradiol concentration (mean = 79.8 pmol/L; range, 23-140 pmol/L); in 16/23 patients, the concentration was even lower than the threshold value for gonadal failure. During the first week of estradiol treatment, depressive symptoms diminished significantly, resulting in a mean MADRS score of 11.0 (Z = -4.20, p < .001), and serum estradiol concentrations approached those of the follicular phase (mean +/- SD = 342 +/- 141 pmol/L). At the end of the second week of treatment, the MADRS scores were compatible with clinical recovery in 19/23 patients.

CONCLUSION: This preliminary study shows that depression symptoms may be rapidly reduced in patients with postpartum depression who have documented estradiol deficiency by treatment with 17beta-estradiol and suggests that estradiol can have significance in the pathophysiology of this condition and may be an option in the treatment of women vulnerable to postpartum depression.

(9) http://www.ncbi.nlm.nih.gov/pubmed/8598756
Lancet. 1996 Apr 6;347(9006):930-3.

Transdermal oestrogen for treatment of severe postnatal depression. by Gregoire AJ, Kumar R, Everitt B, Henderson AF, Studd JW. Mental Health Services, Salisbury Health Care, Salisbury, UK.

BACKGROUND
postnatal depression can have long-term adverse consequences for the mother, for the marital relationship, and for the infant's psychological development. Such depressions can be severe and resistant to both support and counselling and to therapy with antidepressant drugs. We investigated the antidepressant efficacy of oestrogen given transdermally.

METHODS: In a double-blind, placebo-controlled study, 61 women with major depression, which began within 3 months of childbirth and persisted for up to 18 months postnatally, were allocated randomly active treatment (n=34; 3 months of transdermal 17 beta-oestradiol 200 micrograms daily alone, then 3 months with added cyclical dydrogesterone 10mg daily for 12 days each month) or placebo (n=27; placebo patches and tablets according to the same regimen). The women were assessed monthly by self-ratings of depressive symptoms on the Edinburgh postnatal depression scale (EPDS) and by clinical psychiatric interview (schedule for affective disorders and schizophrenia [SADS]-change scale).

FINDINGS: On pretreatment assessments the women in both groups were severely depressed (mean EPDS score 21.8 [SD 3.0] active group, 21.3 [2.9] placebo group; SADS scores, 66.3 [11.4] and 64.3 [10.7]). During the first month of therapy the women receiving oestrogen improved rapidly, and to a significantly greater extent than controls (mean EPDS scores 13.3 [SD 5.7] vs 16.5 [5.3]. Patients receiving placebo also improved over time but, on average, their scores did not fall below the screening threshold for major depression for at least 4 months. The estimated overall treatment effect of oestrogen on the EPDS was 4.38 points (95% Cl 1.89-6.87). None of a range of other factors (age, psychiatric, obstetric and gynaecological history, severity and duration of current episode of depression, and concurrent antidepressant medication), influenced the response to oestrogen.

INTERPRETATION: This study has shown that transdermal oestrogen is an effective treatment for postnatal depression. Further studies are required to establish the minimum effective dose and shortest necessary duration of treatment as well as the mechanism of antidepressant action of oestrogen.

(10) http://www.jabfm.com/cgi/reprint/16/5/372.pdf

The Effectiveness of Various Postpartum Depression Treatments and the Impact of
Antidepressant Drugs on Nursing Infants Dwenda Gjerdingen, MD, MS (J Am Board Fam Pract 2003;16:372– 82.)

Background: Postpartum depression is seen in approximately 13% of women who have recently given birth; unfortunately, it often remains untreated. Important causes for undertreatment of this disorder are providers’ and patients’ lack of information about the effectiveness of various treatments, and their concerns about the impact of treatment on nursing infants. This article presents research-based evidence on the benefits of various treatments for postpartum depression and their potential risks to nursing infants.

There is evidence that postpartum depression improves with antidepressant
drug therapy, estrogen, individual psychotherapy, nurse home visits, and possibly group therapy.

Of the more frequently studied antidepressant drugs in breastfeeding women, paroxetine, sertraline, and nortriptyline have not been found to have adverse effects on infants. Fluoxetine, however, should be avoided in breastfeeding women. By administering effective treatment to women with postpartum depression,
we can positively impact the lives of mothers, their infants, and other family members. (J Am Board Fam Pract 2003;16:372– 82.)

72. Cizza G, Gold PW, Chrousos GP. High-dose transdermal estrogen, corticotropin-releasing hormone, and postnatal depression [letter]. J Clin Endocrinol Metab 1997;82:704.

73. Ahokas A, Kaukoranta J, Wahlbeck K, Aito M. Estrogen deficiency in severe postpartum depression: successful treatment with sublingual physiologic
17B-estradiol: a preliminary study. J Clin Psychiatry 2001;62:332– 6.

74. Ahokas AJ, Turtiainen S, Aito M. Sublingual oestrogen treatment of postnatal depression [letter]. Lancet 1998;351:109.

75. Gregoire AJ, Kumar R, Everitt B, Henderson AF, Studd JW. Transdermal oestrogen for treatment of severe postnatal depression. Lancet 1996; 347:930–3.

76. Ahokas A, Aito M. Role of estradiol in puerperal psychosis. Psychopharmacology (Berl) 1999;147: 108–10.

77. Ahokas A, Aito M, Turiainen S. Association between oestradiol and puerperal psychosis. Acta Psychiatr Scand 2000;101:167–70.

78. Granger ACP, Underwood MR. Review of the role Postpartum Depression Treatment 381 of progesterone in the management of postnatal mood disorders. J Psychosom Obstet Gynaecol 2001;22:49 –55.


Estradiol for Post Partum Psychosis

(11) http://www.ncbi.nlm.nih.gov/pubmed/10817099 
J Clin Psychiatry. 2000 Mar;61(3):166-9. Positive treatment effect of estradiol in postpartum psychosis: a pilot study. Ahokas A, Aito M, Rimón R. Department of Psychiatry, Helsinki City Hospital, Finland.

BACKGROUND: Postpartum illnesses with psychiatric symptoms and serious adverse sequelae are highly prevalent during the childbearing years. Despite multiple medical contacts, these illnesses often remain unidentified and untreated. To study the association between estradiol and puerperal psychosis, we measured serum concentration of estradiol and performed an open-label trial of physiologic 17beta-estradiol in women with this disorder.

METHOD: Ten women with ICD-10 psychosis with postpartum onset consecutively recruited from a psychiatric duty unit were studied. Serum estradiol concentration was measured at baseline and weekly during sublingual 17beta-estradiol treatment for 6 weeks. The treatment effect was evaluated by a clinician-rated psychiatric symptom scale (the Brief Psychiatric Rating Scale [BPRS]).

RESULTS: The baseline serum estradiol levels (mean = 49.5 pmol/L; range, 13-90 pmol/L) were even lower than the threshold value of gonadal failure, and the patients exhibited high scores on the psychiatric symptom scale (mean BPRS total score = 78.3; range, 65-87). During the first week of 17beta-estradiol treatment, psychiatric symptoms diminished significantly (BPRS score decreased to a mean of 18.8, p < .001). Until the end of the second week of treatment, serum estradiol concentrations rose to near the values normally found during the follicular phase, and the patients became almost free of psychiatric symptoms.

CONCLUSION: The reversal of psychiatric symptoms in all patients by treating documented estradiol deficiency suggests that estradiol plays a role in the pathophysiology and may have a role in the treatment of this condition. There was a rebound of psychotic symptoms in the 1 patient who discontinued estradiol treatment. Given the small number of patients, this area deserves further study.

Estradiol for Alzheimers Disease - Improves Cognition

(12) http://www.neurology.org/cgi/content/abstract/57/4/605
Neurology 2001;57:605-612, 2001 American Academy of Neurology

High-dose estradiol improves cognition for women with AD Results of a randomized study by S. Asthana, MD;, L. D. Baker, PhD;, S. Craft, PhD;, F. Z. Stanczyk, PhD;, R. C. Veith, MD;, M. A. Raskind, MD; and S. R. Plymate, MD From Geriatric Research, Education and Clinical Center (GRECC), Veterans Affairs Puget Sound Health Care System

Objective:— To characterize the cognitive and neuroendocrine response to treatment with a high dose of estrogen for postmenopausal women with AD.

Methods:— Twenty postmenopausal women with AD were randomized to receive either 0.10 mg/day of 17ß-estradiol by skin patch or a placebo patch for 8 weeks. Subjects were evaluated at baseline, at weeks 3, 5, and 8 during treatment, and again 8 weeks after treatment termination. During each visit, cognition was assessed with a battery of neuropsychological tests, and blood samples were collected to measure plasma estradiol as well as several other neuroendocrine markers of interest.

Results:— Significant effects of estrogen treatment were observed on attention (Stroop Color Word Interference Test), verbal memory (Buschke Selective Reminding Test), and visual memory (Figure Copy/Memory). In addition, women treated with estrogen demonstrated improved performance on a test of semantic memory (Boston Naming Test) compared with subjects who received a placebo. Estrogen appeared to have a suppressive effect on the insulin-like growth factor (IGF) system such that plasma concentration of IGF binding protein-3 was significantly reduced and plasma levels of estradiol and IGF-I were negatively correlated during estrogen treatment.

Conclusions:— Administration of a higher dose of estrogen may enhance attention and memory for postmenopausal women with AD.  

Anxiety is Strongly Associated with HOT Flashes


(13) http://www.ncbi.nlm.nih.gov/pubmed/15879914

Menopause. 2005 May-Jun;12(3):258-66.

The role of anxiety and hormonal changes in menopausal hot flashes.
Freeman EW, Sammel MD, Lin H, Gracia CR, Kapoor S, Ferdousi T. Department of Obstetrics/Gynecology, University of Pennsylvania, Philadelphia, PA 19104, USA.

OBJECTIVE: To estimate the association of anxiety with menopausal hot flashes in the early transition to menopause.

DESIGN: A randomly identified, population-based cohort of midlife women followed up for 6 years to assess reproductive hormones and other physical, emotional, and behavioral factors. At enrollment, the women were premenopausal, aged 35 to 47 years, and had regular menstrual cycles in the normal range. Enrollment was stratified to obtain equal numbers of African American (n = 219) and white (n = 217) women.

RESULTS: At the 6-year endpoint, 32% of the women were in the early transition stage and 20% reached the late menopausal transition or were postmenopausal. Reports of hot flashes increased with the transition stages, which were determined by bleeding patterns. At endpoint, hot flashes were reported by 37% of the premenopausal women, 48% of those in the early transition, 63% of women in the late transition, and 79% of the postmenopausal women. Anxiety scores were significantly associated with the occurrence of hot flashes and were also significantly associated with the severity and frequency of hot flashes (each outcome at P < 0.001). Compared with women in the normal anxiety range, women with moderate anxiety were nearly three times more likely to report hot flashes and women with high anxiety were nearly five times more likely to report hot flashes. Anxiety remained strongly associated with hot flashes after adjusting for menopause stage, depressive symptoms, smoking, body mass index, estradiol, race, age, and time. In a predictive model, anxiety levels at the previous assessment period and the change in anxiety from the previous assessment period significantly predicted hot flashes (P < 0.001).

CONCLUSIONS: Anxiety is strongly associated with menopausal hot flashes after adjusting for other variables including menopause stage, smoking, and estradiol levels. Anxiety preceded hot flashes in this cohort. Additional studies are needed to examine the duration of menopausal hot flashes and to determine whether treatments that target anxiety effectively reduce menopausal hot flashes.

Estradiol Reduces Anxiety in Mice

(14) http://www.ncbi.nlm.nih.gov/pubmed/19804793

Estradiol reduces anxiety- and depression-like behavior of aged female mice by
Alicia A. Walf and Cheryl A. Frye  Neuroscience Research, The University at Albany-SUNY, United States September 2009

Thus, an acute E2 regimen produced specific anti-anxiety and anti-depressant effects, independent of effects on motor behavior, when administered to aged female C57BL/6 mice.

Estrogen Inhibits Anxiety Through EndoCannabinoid System

http://science.iowamedicalmarijuana.org/pdfs/psych/Hill%202007.pdf
Estrogen recruits the endocannabinoid system to modulate emotionality
Matthew N. Hill, Eda S. Karacabeyli, Boris B. Gorzalka in Department of Psychology, University of British Columbia, 2136 West Mall, Vancouver, BC, Canada V6T1Z4

Estrogen administration elicits anxiolytic and antidepressant-like effects in female rats; however, the mechanism of this effect is unknown. Fatty acid amide hydrolase (FAAH), the enzyme which degrades the endocannabinoid anandamide, has been shown to be regulated by estrogen. Thus, we examined if the anxiolytic and antidepressant effects of estrogen implicated the endocannabinoid system. In the first experiment, ovariectomized female rats were administered a single injection of 17b-estradiol (10 mg) or oil, and 48 h later were given an injection of the cannabinoid CB1 receptor antagonist AM251 (1 mg/kg) or vehicle.

One hour after AM251 or vehicle administration, subjects were tested in either the open field test (OFT), elevated plus maze (EPM) or the forced swim test (FST). Estradiol treatment resulted in a significant increase in open arm entries in the EPM and time spent in the center quadrant of the OFT, which were reversed by co-treatment with  AM251, suggesting that endocannabinoids are integral to the anxiolytic effects of estrogen.

In the second experiment, administration of the FAAH inhibitor URB597 (0.1 and 0.3 mg/kg) increased open arm entries in the EPM and time spent in the center quadrant in the OFT as well as significantly reduced immobility in the FST. Collectively, these data demonstrate that estrogen may elicit changes in emotional behavior through an endocannabinoid mechanism, and suggest that inhibition of FAAH represents a therapeutic target for anxiety and depression in women.


(15) http://www.ncbi.nlm.nih.gov/pubmed/15474758
Maturitas. 2004 Oct 15;49(2):140-7.

A short study in the treatment of hot flashes with buccal administration of 17-beta estradiol. Gass MS, Rebar RW, Cuffie-Jackson C, Cedars MI, Lobo RA, Shoupe D, Judd HL, Buyalos RP, Clisham PR.

OBJECTIVE: To assess the efficacy and safety of 17-beta estradiol buccal tablets in reducing hot flush frequency (HFF) in postmenopausal women. METHODS: Estradiol buccal tablets containing 0.05, 0.1, 0.2, or 0.4 mg or placebo were administered for 28 days to 99 postmenopausal women in a randomized, double-blind study; 19 premenopausal women were studied concurrently for comparison of laboratory data. Objective and subjective assessments of HFF were obtained along with measures of estradiol, estrone, follicle-stimulating hormone (FSH), and luteinizing hormone (LH). RESULTS: Measurements of HFF revealed significant decreases from baseline in all estradiol groups (P < 0.01). In the 0.4 mg group, HFF decreased significantly compared to placebo (P < 0.01). All estradiol doses produced similar improvement in the vaginal maturation index. Mean serum estradiol levels increased as doses increased but were lower than in the premenopausal subjects. Mean serum FSH and LH levels decreased in all estradiol groups but not to the levels of the premenopausal subjects; the greatest decrease occurred at the two highest estradiol doses. CONCLUSION: A numerical dose-response relationship with hot flushes was seen in this pilot study comparing 0.05, 0.1, 0.2, and 0.4 mg buccal estradiol. Only 0.4 mg 17-beta estradiol significantly reduced the occurrence of hot flushes compared to placebo.

(16) http://www.ncbi.nlm.nih.gov/pubmed/11400216
Menopause as a Measure of Population Health - Physiology of hot flashes Robert R. Freedman 1 2  Am. J. Hum. Biol. 13:453-464, 2001

Hot flashes are the most common symptom of the climacteric, although prevalence estimates are lower in some rural and non-Western areas. The symptoms are characteristic of a heat-dissipation response and consist of sweating on the face, neck, and chest, as well as peripheral vasodilation. Although hot flashes clearly accompany the estrogen withdrawal at menopause, estrogen alone is not responsible since levels do not differ between symptomatic and asymptomatic women. Until recently it was thought that hot flashes were triggered by a sudden, downward resetting of the hypothalamic setpoint, since there was no evidence of increased core body temperature. Evidence obtained using a rapidly responding ingested telemetry pill indicates that the thermoneutral zone, within which sweating, peripheral vasodilation, and shivering do not occur, is virtually nonexistent in symptomatic women but normal (about 0.4°C) in asymptomatic women. The results suggest that small temperature elevations preceding hot flashes acting within a reduced thermoneutral zone constitute the triggering mechanism. Central sympathetic activation is also elevated in symptomatic women which, in animal studies, reduces the thermoneutral zone. Clonidine reduces central sympathetic activation, widens the thermoneutral zone, and ameliorates hot flashes. Estrogen virtually eliminates hot flashes but its mechanism of action is not known. . © 2001 Wiley-Liss, Inc.

(17) http://jcem.endojournals.org/cgi/content/abstract/61/4/627
Journal of Clinical Endocrinology & Metabolism Vol. 61, No. 4 627-632

Treatment of Hot Flashes with Transdermal Estradiol Administration*
KENNETH A. STEINGOLD, LARRY LAUFER, RYSZARD J. CHETKOWSKI, JOHN D. DEFAZIO, DENNIS W. MATT, DAVID R. MELDRUM and HOWARD L. JUDD  Department of Obstetrics and Gynecology, University of California, Los Angeles, School of Medicine Los Angeles, California 90024

A randomized prospective double blind study was performed to assess the ability of a transdermal therapeutic system (TTS) delivering estradiol (E2) to suppress hot flashes (HFs) in symptomatic postmenopausal women. Patients were given placebo or E2 in four doses for a 20-day period, and serum gonadotropin and estrogen levels and the occurrences of HFs were measured.

Administration of placebo had no measurable effect on either estrogen or gonadotropin levels or the occurrence of HFs. A dose-response relationship was found between the rate of E2 administered and the circulating level of E2, with 25, 50, 100, and 200 µ/24 h dosages raising the mean E2 concentrations from mean baseline levels of 5-8 pg/ml to 18, 38, 73, and 100 pg/ml, respectively. Estrone levels also increased with TTS application, but to a lesser extent than did E2 levels. Doseresponse reductions of FSH and LH with increasing amounts of E2 administration occurred, but gonadotropin levels were not lowered in any of the patients into the ranges found in premenopausal women. TTS application significantly suppressed the occurrence of HFs at the 50 Mg/24 h dosage and higher. A significant negative correlation (r = 0.6045; P < 0.001) between E2 levels and the rates of occurrence of HFs was found during hormone administration. Based on this regression, 50% and100% reductions of HFs should occur at 61 and 122 pg/ml E2. These data indicate that the transdermal delivery of E2 with these systems significantly reduced the occurrence of HFs and allowed definition of the therapeutic range of hormone replacement in terms of lost ovarian function, as reflected by circulating E2 levels.