Menopause is defined as the absence of menstruation for 12 months without a pathological cause and it is marked by physical fluctuations and biological changes that can impact women's quality of life. During the perimenopause and menopause transition period, women may experience a variety of changes, including menstrual cycle irregularity and climacteric symptoms. Treatment to relieve symptoms may include hormonal and non-hormonal options, such as behavioral therapies, medications and low-dose hormonal therapies. The objective of this study will be to evaluate the effect of melatonin in women with perimenopausal symptoms. This is a double-blind, placebo-controlled randomized clinical trial research, where perimenopausal women will be interviewed, who will answer questionnaires, and will use melatonin/placebo for a period of 30 days, before and after, they will be asked about possible changes during treatment, such as mood changes, drowsiness, dizziness, headaches or allergic reactions. It is hoped that with this study, the effect of melatonin in women on climacteric symptoms during the perimenopausal period will be understood.

This is a randomized, double-blind, parallel, placebo-controlled clinical trial. 40 patients will be recruited to participate in the study, 20 of whom will receive the treatment and 20 will receive the placebo for a period of 30 days.Before and after, they will be asked about possible changes during treatment, such as mood changes, drowsiness, dizziness, headaches or allergic reactions.

The study will be carried out at the São Cristóvão Basic Health Unit in Lajeado - RS. The research and invitation to participate will also be publicized through the University of Vale do Taquari's social media, through an informative/explanatory text. Data collection from these participants will be carried out at their homes or in a location that suits them best by arrangement. If the participant has travel expenses for their participation, travel/transportation costs will be reimbursed within the project budget, which will be the responsibility of the responsible researcher.

The study protocol was submitted and approved by the Univates Health Research Ethics Committee by CAAE: 70400923.9.0000.5310 and opinion no.: 6.131.475.

For statistical analyzes the statistical program JAMOVI (Version 2.3) [Computer Software] (2022) and R Core Team (2021) will be used. The Kolmogorov Smirnov and Shapiro-Wilk Test will be used to verify the normality of the data. Non-parametric samples will be analyzed using the Mann-Whitney U test and parametric t-test. Continuous variables will be presented as mean±SD. The number and percentage will be presented as n (%), and numerical data will be analyzed using the Chi-square test (χ²) and/or Fisher's exact test. The Confidence Interval value (IC95%) will be provided. The value of p<0.05 will be considered statistically significant.

Inclusion Criteria:- Being female and in peri-menopause, experiencing an irregular menstrual cycle, having had at least one menstrual period in the last 6 months.

• Age 45 years or older
• Be literate

Exclusion Criteria:-History of alcohol or other substance abuse in the last 6 months

• Use of hormonal therapy;
• Neurological disease;
• Oncological disease;
• Ischemic heart disease;
• Liver failure;
• Renal insufficiency;
• Use of central nervous system medications (antidepressants, anticonvulsants, antipsychotics and benzodiazepines)

To control possible measurement biases, in the present study, the following measures will be taken: for the pharmacological intervention (use of melatonin or placebo), the evaluators and patients will be blinded to the intervention. The randomization codes will remain in the care of two evaluators not involved in the care of the patients, which allows better control of manipulations to favor any intervention to be carried out. Patients will be instructed to discuss all aspects related to pharmacological interventions with the researcher during treatment. The sealed envelope method will be used for confidential allocation. Before the recruitment phase, envelopes containing protocol materials will be prepared. Each envelope containing the allocated treatment will be sealed and numbered sequentially. After each participant agrees to participate in the study, the envelope will be opened and the results will be reported to the researcher who will carry out the interventions.