Menorrhagia is the medical term for abnormally heavy or prolonged menstrual bleeding. A period is considered heavy if the blood loss disrupts daily life, such as soaking through protection hourly or lasting longer than seven days. The menstrual cycle relies on cyclical hormone fluctuations that regulate the growth and breakdown of the uterine lining. When this hormonal balance is disrupted, it often causes excessive uterine blood loss.
Estrogen and Progesterone: The Regulators of Uterine Lining
The monthly cycle is governed by the interplay between estrogen and progesterone. Estrogen dominates the first half, stimulating the proliferation of cells and blood vessels to thicken the endometrium, the lining of the uterus.
Following ovulation, the corpus luteum produces progesterone, which stabilizes the estrogen-primed lining. Progesterone converts the endometrium into a mature, secretory lining by limiting growth. If pregnancy does not occur, both hormone levels decline, triggering the shedding of the endometrium.
Heavy periods often result from unopposed estrogen, where estrogen levels are high relative to progesterone. This imbalance occurs during anovulatory cycles when an egg is not released, meaning no corpus luteum forms to produce progesterone. Without progesterone, the endometrium grows excessively, leading to endometrial hyperplasia, or an abnormally thick lining.
When this overbuilt lining sheds, the increased tissue volume results in a heavier and more prolonged menstrual flow. Hormonal contraception, which provides progesterone-like compounds, is often used to regulate uterine lining thickness and reduce blood loss.
Systemic Hormones That Influence Menstrual Flow
Systemic endocrine glands also influence menstrual blood volume. The thyroid gland produces hormones that regulate metabolism and influence the reproductive system. Hypothyroidism (an underactive thyroid) is associated with heavy menstrual bleeding.
Low thyroid hormone levels disrupt the liver’s ability to metabolize sex hormones, potentially increasing circulating estrogen. Severe hypothyroidism can also increase thyrotropin-releasing hormone (TRH), which stimulates the pituitary gland to release prolactin.
Elevated prolactin (hyperprolactinemia) suppresses the production of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). This prevents ovulation, leading to an anovulatory cycle where progesterone is not produced, resulting in the unopposed estrogen state that causes heavy bleeding.
Local Hormonal Mediators of Bleeding Control
Bleeding control during menstruation is managed by substances acting locally within the endometrial tissue. Prostaglandins, lipid compounds, are important local mediators of uterine hemostasis. They are released as the lining breaks down, playing a role in blood vessel constriction and uterine muscle contraction.
Two prostaglandins, Prostaglandin F2\(\alpha\) (PGF2\(\alpha\)) and Prostaglandin E2 (PGE2), are relevant to menstrual flow. PGF2\(\alpha\) is a potent vasoconstrictor and stimulates uterine muscle contractions, both necessary to stop bleeding. In contrast, PGE2 and Prostacyclin (PGI2) are vasodilators that widen blood vessels and inhibit platelet aggregation.
In women with menorrhagia, research shows an abnormally low ratio of PGF2\(\alpha\) to PGE2 and PGI2 in the endometrium. This imbalance suggests a lack of necessary vasoconstrictive and clotting agents, preventing the effective cessation of bleeding once the lining is shed. This localized imbalance explains why non-hormonal medications that inhibit prostaglandin synthesis can reduce menstrual flow.
When to Seek Diagnosis and Medical Advice
Consult a healthcare provider if menstrual bleeding is consistently disruptive. Warning signs include soaking through one or more sanitary pads or tampons every hour for several consecutive hours. Passing blood clots larger than a quarter or bleeding for longer than seven days also indicates a need for medical evaluation.
Excessive blood loss can lead to iron deficiency anemia, manifesting as persistent fatigue, weakness, or shortness of breath. A physician will take a thorough history and perform blood tests, including a complete blood count to check for anemia and specific hormone level checks, such as Thyroid-Stimulating Hormone (TSH) and prolactin.
While hormonal imbalance is a frequent cause, the doctor will also perform examinations to rule out structural issues. These include uterine fibroids or polyps, which are non-hormonal but also cause heavy bleeding. A focused diagnostic approach helps pinpoint the specific cause, ensuring the most appropriate course of action is recommended.