Oxytocin and Reward Processing in Women

What Was Tested

In this not phased trial, researchers set out to test Oxytocin.

Oxytocin is a hypothalamic neuropeptide that is best known for its peripheral physiological effects in the female organism i.e., uterine contractions during birth.

The neuropeptide furthermore affects reward processing and metabolic functions such as eating behavior and body weight.

It had four arms (groups): NC follicular (experimental), NC luteal (experimental), OC combined (experimental) and OC progestogen-only (experimental).

Naturally cycling, healthy women in the follicular menstrual cycle phase.

Naturally cycling, healthy women in the luteal menstrual cycle phase.

Healthy women taking combined oral hormonal contraceptives.

The registry classes the interventions as drug.

More on the Plan

All participants will take part in an intake session (T0) and two experimental sessions (T1 and T2) scheduled approximately four weeks apart.

In the intake session (T0) the eligibility of the participants i.e., MRI compatibility, will be verified.

Additionally, the participants will be asked to fill out questionnaires i.e., regarding their personality, sleep and eating behavior and perform standardized cognitive tests.

The investigators will obtain sex steroids (e.g., progesterone, estrogen, testosterone) i.e., to verify the menstrual cycle phase, synthetic steroids (e.g., ethinylestradiol, levonorgestrel) and metabolic hormones (e.g., glucose, insulin, c-peptide) from blood samples in the two experimental sessions.

Who Took Part

Enrollment: 100 planned participants were the target.

It was open to women only aged from 18 years up to 40 years.

Healthy volunteers could join, not only people with the condition.

Examples of who could join: Body-mass index (BMI): 18-28 kg/m2. Sex: female (since birth). Normal or corrected vision. Natural menstrual cycle (NC) or intake of hormonal oral contraceptives (OC). NC: No hormonal contraception for at least 6 months; regular menstrual cycle (between 25 and 31 days) prior to participation.

The full record lists 6 inclusion and 20 exclusion criteria; among the exclusions: current neurological or psychiatric disease (anamnestic survey); current medical problems such as hormonal, metabolic, or chronic diseases (e.g., severe hypertension, diabetes, dysfunctions of the thyroid, or congestive heart failure); pregnancy, delivery and lactation (current and within the last year; anamnestic survey, current pregnancy test).

How the Study Was Run

It was run as a randomized, crossover and triple-blind study.

Because people in this Oxytocin study were split into groups at random, differences between the groups are less likely to reflect who happened to join each one.

In the crossover set-up each of the participants took both Oxytocin and the comparison in turn, acting as their own control.

Neither the participants nor the staff measuring them knew who was on Oxytocin, so expectations could not easily colour the readings.

Those kept unaware of assignments: participant, investigator and outcomes assessor.

It started in 2024-02-16 with completion listed for 2026-12-31.

It ran at 1 site in Germany.

Its stated primary purpose is basic science.

What Was Measured

The main thing measured (primary outcome): Oxytocin and sex hormone level induced changes in reward-related brain responses in the reward circuitry during effort-based decision making. Oxytocin induced changes in reward related behavior. Oxytocin induced changes in eating behaviour (time frame: During the experimental session (approximately 4.5 hours)).

It also tracked 3 secondary outcomes, for example Oxytocin induced changes in functional connectivity, Oxytocin induced changes in stress-axis reactivity and Sex hormone induced changes in energy expenditure.

What This Means in Plain Language

Put simply, this is a not phased, randomized trial of Oxytocin in 100 people.

It is still recruiting; no results are posted to the registry yet, so nothing here describes outcomes.

More context: the Oxytocin compound page, all human trials.