This purpose of this study is to understand the types of bacteria that are in the bladder and vagina in patients with overactive bladder (OAB) symptoms and understand if the types of bacteria change when with the use of estrogen in the vagina. The investigators are also trying to understand how estrogen influences the body's ability to make substances called peptides that can kill bacteria.

Overactive bladder (OAB) syndrome is characterized by the symptom complex of urinary urgency, usually with associated frequency and nocturia, with or without urgency urinary incontinence in the absence of infection or other pathology. OAB affects approximately 31% of women over the age of 65. Vaginal estrogen, a well-documented treatment for OAB in hypoestrogenic women, has been shown to improve symptoms of frequency, urgency and urgency urinary incontinence (UUI). Several theories have been proposed to explain the mechanism underlying estrogen's effect on lower urinary tract symptoms (LUTS). The investigators propose that estrogen treatment influences bacterial communities (microbiomes) in the vagina and bladder and alters urothelial and vaginal (AMPs) thereby improving OAB symptoms in hypoestrogenic women.

Long-standing medical dogma has been replaced by clear evidence that a female urinary microbiome (FUM) exists. The investigators recently reported that the FUM in women without OAB is less diverse than the FUM of women with OAB. The investigators soon will report that FUM status stratifies women with OAB into treatment response groups and women with less diverse FUMs are more likely to respond to anti-cholinergic OAB therapy (Thomas-White et al., in preparation). This suggests that the FUM is a factor in lower urinary tract symptoms (LUTS) and that FUM diversity contributes to LUTS and treatment response, like the vaginal microbiome and its contribution to vaginal symptoms.

In hypoestrogenic women, the vaginal microbiome shifts from low diversity communities, commonly dominated by Lactobacillus, to more diverse communities dominated by anaerobes; this change can be reversed with estrogen treatment. Since the FUM of women with OAB includes bacteria similar to those of the vaginal microbiome (e.g. Lactobacillus, Gardnerella, and diverse anaerobes), the investigators reason the FUM would respond similarly to estrogen and become less diverse. Although transvaginal medications likely alter nearby bacterial niches (e.g. the bladder), no study has reported the urinary microbiomic response to vaginal estrogen.

While almost nothing is known about urinary/vaginal microbiome interplay, even less is known about immune response modulation in the bladder and vagina. However, estrogen reduces the subsequent urinary tract infection (UTI) rate in hypoestrogenic women affected by recurrent UTI, and estrogen induces urothelial antimicrobial peptide (AMP) expression. Since AMPs exhibit microbicidal activity, stimulate inflammation, and facilitate epithelial barrier homeostasis, estrogen may work through AMPs as mediators to optimize microbial equilibrium.

The investigators hypothesize that, following estrogen treatment of hypoestrogenic women with OAB, symptom improvement will be associated with 1) reduced FUM diversity, 2) alteration of other FUM characteristics and 3) increased AMP levels. The investigators propose two specific aims:

Aim 1: To compare pelvic floor microbiome (PFM) diversity and AMP levels before and after estrogen treatment in hypoestrogenic women with OAB symptoms.

Aim 2: Determine if FUM characteristics correlate with OAB symptoms.

Inclusion Criteria:

• Women who present with symptoms of OAB, defined as a condition characterized by urgency, with or without urgency incontinence, usually with frequency and nocturia in the absence of obvious pathology or infection [9], with atrophic vaginitis.
• Postmenopausal by history (i.e., defined as twelve months or greater since last menstrual period), surgical menopause with removal of bilateral ovaries, or age over 55 with a previous hysterectomy (without removal of bilateral ovaries).
• English language skills sufficient to complete questionnaires
• Clinical indication for vaginal estrogen use (i.e., hypoestrogenic findings on physical examination)
• Patients not currently receiving vaginal estrogen therapy

Exclusion Criteria:

• Patients currently on systemic hormone replacement therapy (HRT) or who have been on HRT within the past three months
• Patients with current diagnosis or history of estrogen dependent malignancies (e.g., breast or endometrial malignancies)
• Contraindication or allergy to estrogen therapy
• Insufficient English language skills to complete study questionnaires
• Women with active, standard culture positive urinary tract infection at baseline assessment, or those with a urine dip positive for leukocytes and nitrates on straight catheterized sample.
• Patients who have received antibiotics within the past two weeks
• Patients with stage 3 or 4 pelvic organ prolapse based on the pelvic organ prolapse quantitation system (POP-q)
• Patients unwilling to use vaginal estrogen preparation
• Patients currently on anticholinergic medications or who have received anticholinergic medications within the past three months
• Patients who have previously failed two medications for treatment of OAB or have previously received more advanced treatment for OAB including intra-vesicle botulinum toxin injections, posterior tibial nerve stimulation, or implantation of a sacral neuromodulator
• Patients wishing to start anticholinergic medication at the initial encounter
• Undiagnosed abnormal genital bleeding
• Active deep vein thrombosis (DVT), pulmonary embolism (PE), or a history of these conditions
• Active arterial thromboembolic disease (for example, stroke and MI), or a history of these conditions
• Known liver dysfunction or disease
• Known protein C, protein S, or antithrombin deficiency or other known thrombophilic disorders

12 weeks