Hypothyroidism causes heavy periods in women, according to Mayo Clinic. The condition mostly affects women who are middle-aged or older, though people of any age can contract it.
Hashimoto's disease is the most common cause of hypothyroidism, according to Womenshealth.gov. This is an autoimmune disease where the body attacks its own thyroid gland. Because of this, the gland does not produce enough thyroid hormone. Other causes of hypothyroidism are treatment for an overactive thyroid, the removal of the thyroid altogether or damage to the thyroid caused by radiation.
Other symptoms of hypothyroidism include weight gain, even though the patient has not increased her caloric intake, and intolerance of cold, according to Womenshealth.gov. The patient may also suffer from constipation, skin that is pale and dry, a hoarse voice, puffy face, fatigue and depression. Her muscles may be weak or painful, she may also suffer pain in her joints and she may also have a high LDL cholesterol count.
People who have hypothyroidism are treated with levothyroxine, a synthetic form of the T4 thyroid hormone, claims Womenshealth.gov. This medication usually stimulates the body into making T3, another thyroid hormone, though a synthetic form of T3 is also available. Patients sometimes receive the synthetic forms of both drugs.