Oligomenorrhea is the medical term for infrequent menstrual periods, a common type of menstrual irregularity. A normal menstrual cycle typically occurs every 21 to 35 days, but with this condition, cycles extend beyond 35 days, resulting in fewer than nine periods annually. Understanding the causes behind this change is important for reproductive health, as this pattern often signals an underlying physiological shift.
Understanding Secondary Oligomenorrhea
Secondary oligomenorrhea refers to the development of infrequent periods in a person who previously established a pattern of normal, regular menstrual cycles. This is distinct from primary oligomenorrhea, where regular cycles were never established from the onset of menstruation.
The change in cycle frequency indicates a disruption along the hypothalamic-pituitary-ovarian (HPO) axis, the complex signaling pathway that controls the reproductive system. The “secondary” nature implies that an external factor or a newly developed internal condition has imposed a physiological stressor on this axis. This change in the hormonal environment means the ovary is no longer receiving the necessary signals to consistently trigger ovulation and subsequent menstruation.
Common Causes and Contributing Factors
The most frequent underlying cause identified in people with infrequent periods is Polycystic Ovary Syndrome (PCOS), a complex endocrine disorder. PCOS is characterized by an imbalance of reproductive hormones, including elevated levels of androgens, often leading to a lack of regular ovulation. An estimated 75% to 85% of individuals diagnosed with PCOS experience this pattern of infrequent cycles.
Disruptions in the function of the thyroid gland also commonly contribute to the condition, as both an underactive (hypothyroidism) or an overactive (hyperthyroidism) gland can interfere with the HPO axis. Another hormonal issue is hyperprolactinemia, where an excess of the hormone prolactin, often produced by the pituitary gland, suppresses the release of gonadotropin-releasing hormone (GnRH). This suppression then prevents the ovary from developing and releasing an egg.
High levels of chronic psychological or physical stress can alter the cycle by increasing the production of the stress hormone cortisol. Elevated cortisol can inhibit GnRH release from the hypothalamus, essentially putting the reproductive system on hold. Rapid or extreme changes in body weight, whether significant weight gain or dramatic weight loss, also affect the body’s fat stores and the production of hormones like leptin and estrogen, which are needed for normal menstrual function.
Intense, high-volume exercise, particularly in endurance athletes, can also lead to infrequent cycles. This rigorous physical activity, especially when combined with insufficient caloric intake, creates an energy deficit that signals the body to conserve resources. This energy drain disrupts the hormonal balance required to sustain a consistent menstrual cycle.
How Doctors Diagnose the Condition
Diagnosis begins with a thorough medical history to establish the pattern of irregularity, specifically confirming that regular cycles were previously present to meet the “secondary” criteria. A physical examination will also be performed, which includes checking for signs of hormonal excess, such as acne or excessive hair growth. The first and simplest diagnostic step is typically a pregnancy test to rule out gestation as the cause of a missed period.
Following this, a series of blood tests are ordered to evaluate the levels of reproductive and related hormones. This panel usually includes thyroid-stimulating hormone (TSH) to check for thyroid dysfunction, prolactin, and the gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Levels of androgens, such as testosterone, may also be measured if symptoms like hirsutism are present.
Imaging studies are often necessary, most commonly a pelvic ultrasound. This procedure allows the physician to visualize the ovaries to check for multiple small cysts, a common finding in PCOS. The ultrasound also assesses the thickness of the uterine lining, which is an important indicator for long-term health risks associated with a lack of regular shedding.
Managing and Treating Infrequent Periods
Treatment for secondary oligomenorrhea is always focused on resolving the specific underlying cause identified during the diagnostic process. If a thyroid disorder is found, medication to correct the thyroid hormone levels, such as levothyroxine for hypothyroidism, is the primary intervention. For people diagnosed with PCOS, management often involves medications like metformin to improve insulin sensitivity, which in turn can help regulate the menstrual cycle.
For those not seeking pregnancy, hormonal management is a direct way to restore cycle regularity and protect the uterine lining. Combined hormonal contraceptives, such as birth control pills, provide a consistent level of hormones to override the HPO axis disruption and ensure a withdrawal bleed. Alternatively, progestin therapy can be administered periodically to induce a bleed and prevent the excessive buildup of the endometrial tissue, which can be a health concern when periods are infrequent.
Lifestyle modifications are a foundational part of managing many underlying causes of the condition. This includes working toward achieving a healthy body weight, as both extreme underweight and obesity can disrupt hormonal balance. People who engage in high-intensity exercise may be advised to reduce the volume or intensity of their training, and effective stress management techniques are encouraged to lower cortisol’s impact on the reproductive system.