The project aimed at identifying neuropsychobiological signatures of pharmacological sex-steroid hormone manipulations in healthy women as a risk model for depression.

The study is a double-blind, randomized, placebo-controlled study. Investigators included 63 healthy female volunteers with regular menstrual cycles between 23 and 35 days. Participants were randomized to active Gonadotrophin-Releasing-Hormone agonist (GnRHa) (goserelin 3.6 mg implant) or placebo (saline injection) intervention, which was initiated in the mid follicular phase (i.e. cycle day 22.6 ±2.5). Sixty women completed follow-up and entered the analyses, except for a few drop outs on some domains. The following domains were addressed at baseline and at follow-up (16±3 days post intervention), (which corresponded to the early ovarian suppression phase of the biphasic hormone response to GnRHa): 1) serotonin transporter binding as imaged by 11CDASB Positron Emission Tomography (PET), 2) functional Magnetic Resonance Imaging (fMRI) emotional processing, 3) fMRI reward processing, 3) rating state fMRI (rsfMRI), 4) structural MRI, 5) Neuropsychology, 6) Psychophysiology, 7) Hypothalamus-Pituitary-Adrenal cortex (HPA)-axis dynamics, 8) Peripheral markers of immunoactive cell responses, 9) Epigenetic factors.

Psychometrics in terms of self reported mental distress and interview based ratings were monitored across the intervention period to monitor potential symptoms of mental distress and psychopathology. Also ovarian hormone responses, peripheral blood markers, and side effects scores were collected across the intervention period.

Aims and hypotheses:

Gender matters in normal brain function as well as in neuropsychiatric disorders. E.g. the vulnerability to mood and anxiety disorders is considerably greater in women. Among other factors, this possibly reflects gender differences in central serotonergic function since dysfunction of serotonergic neurotransmission is critically involved in the pathophysiology of mood and anxiety disorders, schizophrenia, and Alzheimer's disease. In particular, women going through phases in life where sex hormones decline rapidly from high levels or fluctuate, have a higher frequency of severe mood state changes and are more vulnerable to psychiatric disorders, e.g. across the pre to postpartum and menopausal transition. Interestingly, this risk is associated with increased variability of the plasma levels of the sex-hormone estradiol. Therefore, sex-hormone manipulation with a pharmacologically induced biphasic ovarian hormone response serve as a unique opportunity to study how sex-hormone fluctuations provoke mood state changes and increase vulnerability to neuropsychiatric disorders.

In this project investigators aimed at investigating whether sex-hormone manipulation affects: 1. Molecular imaging markers of serotonergic neurotransmission in vivo, 2. Brain structure, architecture and functional connectivity, 3. Stress and inflammatory responses, and 4. Cognitive functions, emotional processing, and information filtering, of importance in the pathophysiology of neuropsychiatric disorders.

Mentally healthy female volunteers were assessed at baseline (i.e cycle day 6.6 ±2.2) and at follow-up (i.e 16.2 ±2.6 days post intervention) in the early ovarian suppression phase af a Gonadotrophin-Releasing-Hormone agonist response in a placebo-controlled, double-blinded design (cohort size aim: N=30x2).

Research in neurobiological correlates of vulnerability related to sex-hormone changes is pivotal to improve the etiological understanding of brain disorders with gender differences in their incidence and/or nature. Such research may contribute to ameliorate fertility treatment, to improve treatment of mood disorders and schizophrenia, and, ideally, shed light on possible preventive strategies in vulnerable phases of women's lives such as the pre- to post-partum and menopausal transition period.

Hypotheses:

Investigators hypothesised that sex-hormone manipulation is associated with the following: 1. Compromised serotonergic neurotransmission, 2. Changes in functional and structural connectivity and lower hippocampal brain volumes and/or markers of decreased neurogenesis, 3. Increased stress reactivity and inflammatory responses, and 4. Changes in neurocognitive functioning and negative bias in emotional processing and information filtering. Investigators further hypothesised that these changes occur in a manner dependent on the magnitude of the estradiol drop from baseline and dependent on symptoms of depressed and anxious mood.

General study design:

The study is a prospective, double-blinded, placebo-controlled, combined within-subject and between-group design of neuropsychobiological changes in response to hormonal down-regulation. The investigation program will be performed at baseline in the mid-follicular phase, at day 5-8 of the menstrual cycle, and in the down-regulated state, 14-19 days after GnRHa intervention.

Participants. Investigators aimed at including 60 healthy female volunteers, in the age range 18-40 years. Group 1 (N=30) will receive sex-hormone manipulation with GnRHa, and group 2 (N=30) will receive placebo (saline injection). The inclusion will be stratified according to a polymorphism in the serotonin transporter promoter region (5-HTLPR).

The investigation program includes functional brain imaging of the serotonin transporter with [11C]DASB PET (6) and fMRI, structural brain imaging, blood measurements of sex-hormone levels, inflammatory and epigenetic biomarkers, characterization of the cortisol awakening response, and psychophysiological measures of information processing, and monitoring of symptoms of mental distress and psychopathology across the intervention period. An initial screening program will secure inclusion of healthy controls only and determine trait parameters such as genotypes, IQ and personality measures.

The study was registered at and approved by the Danish Ethical Committee before participant inclusion under the protocol identification number: H-2-2010-108. All participants gave written informed consent.

Inclusion Criteria:

• Healthy women
• Regular menstrual cycles (23 -35 days cycle length)
• No systemic or intrauterine steroid hormone use

Exclusion Criteria:

• Psychiatric disorder (DSM IV Axis I or WHO ICD-10 diagnostic classification).
• Prior or present neurological or other severe medical condition including substance abuse.
• No drug intake suspected to influence results
• Conditions that may increase risk by participating in the study program including ovarian cysts
• Pregnancy during the last year
• Delivery during the last 2 years
• Presently wishing to obtain pregnancy
• Breast feeding
• Not fluent in Danish or severe visual or hearing impairments
• Earlier or present learning disabilities
• Claustrophobia (due to MRI scans)
• Metal implants (excludes MRI)

Via database of Center for Integrated Molecular Brain Imaging (Knudsen et al 2016, NeuroImage) data will be available for neuroscience research community contingent on approval by scientific board