According to Dr. Duong Ngoc Hung, Master of Science, from the Obstetrics and Gynecology Unit at Tam Anh Cau Giay General Clinic, the menstrual cycle reflects the activity of the hypothalamic-pituitary-ovarian endocrine axis. In adult women, cycles typically range from 21-35 days. Menstruation may arrive a few days early or late due to changes in lifestyle, psychology, or sleep. However, if delayed menstruation is prolonged and recurs over multiple cycles, after ruling out pregnancy, this condition may be related to endocrine or gynecological diseases.

Prolonged mental stress, lack of sleep, overwork, or chronic anxiety can alter the brain's signals that regulate reproductive hormones. This often delays ovulation, causing menstruation to arrive late or even not appear within a cycle. If stress is the primary cause, the cycle can stabilize once the individual gets sufficient sleep, reduces pressure, eats regularly, and engages in light exercise.

Adipose tissue plays a role in the metabolism of female sex hormones. When body fat levels change too rapidly, hormone concentrations become imbalanced, leading to delayed or absent ovulation. Individuals on strict diets, fasting, engaging in high-intensity exercise, or experiencing rapid weight loss are prone to delayed or infrequent menstruation. Conversely, being overweight or obese also increases the risk of ovulatory dysfunction, especially in women with insulin resistance or polycystic ovary syndrome. Weight adjustment should be gradual, with nutritional or medical consultation if menstrual irregularities are present.

Individuals with polycystic ovary syndrome have higher-than-normal levels of male hormones, disrupting the menstrual cycle; in some cases, menstruation may occur only two to three times a year. Without proper monitoring, this condition can affect fertility and increase the risk of metabolic disorders.

Doctor Hung examines a woman. Photo: Tam Anh General Hospital

Certain medications can alter the menstrual cycle, including hormonal contraceptives, emergency contraception, antidepressants, sedatives, corticosteroids, or drugs for chronic diseases. After discontinuing hormonal contraceptives, the body may also require several months for the cycle to self-regulate. If delayed menstruation occurs after starting new medication, individuals should consult their doctor. Do not discontinue medication independently, especially those for underlying conditions, as this can impact health more significantly than menstrual irregularities.

Regular exercise benefits health, but high-intensity physical activity combined with insufficient energy intake can reduce the hormonal signals necessary for ovulation. This condition is common among athletes, heavy gym-goers, long-distance runners, or individuals experiencing rapid weight loss. Individuals may experience delayed or infrequent menstruation, fatigue, weight loss, and insomnia. If prolonged, amenorrhea (absence of menstruation) due to excessive exercise can affect bone density and fertility.

In women over 40, delayed or irregular menstruation can signal perimenopause. Ovarian activity gradually declines, and estrogen hormone levels fluctuate, leading to cycles that are sometimes short, sometimes long, with changes in menstrual blood flow. Some individuals also experience hot flashes, night sweats, difficulty sleeping, and vaginal dryness.

The thyroid gland produces hormones involved in regulating metabolism. When the thyroid gland is overactive or underactive, the menstrual cycle can be affected. Hypothyroidism (underactive thyroid) causes delayed, infrequent, or prolonged menstruation, along with fatigue, weight gain, dry skin, and constipation. Hyperthyroidism (overactive thyroid) often leads to palpitations, weight loss, hand tremors, difficulty sleeping, and lighter or less frequent periods.

Prolactin is a hormone associated with milk production. When prolactin levels rise outside of pregnancy or breastfeeding, ovulation can be suppressed, leading to delayed or absent menstruation. Causes may include medication, endocrine disorders, or a prolactin-secreting pituitary tumor. Suggestive signs include abnormal milk discharge, headaches, blurred vision, and decreased libido.

Certain conditions such as ovarian tumors, premature ovarian insufficiency, pelvic inflammatory disease, intrauterine adhesions after procedures, chronic kidney or liver disease, diabetes, and eating disorders can also cause irregular menstruation. Premature ovarian insufficiency, in particular, warrants attention in women under 40 who experience infrequent or absent periods, hot flashes, difficulty sleeping, decreased libido, or difficulty conceiving. Delayed menstruation caused by underlying medical conditions is often not an isolated symptom; it may also be accompanied by lower abdominal pain, abnormal vaginal discharge, painful intercourse, or unexplained weight loss or gain.

Doctor Hung advises that women experiencing a few days of delayed menstruation, a negative pregnancy test, and no other unusual symptoms can monitor their condition further. However, women should seek medical attention if menstruation is delayed for over two to three months, cycles are consistently longer than 35 days, or if they experience abnormal vaginal bleeding, severe lower abdominal pain, unusual milk discharge, headaches with blurred vision, or excessive hair growth.

Van Anh