How Do Selective Estrogen Receptor Modulators Work?

Selective estrogen receptor modulators (SERM) are a class of medications used to relieve postmenopausal symptoms and to prevent bone loss (osteoporosis) associated with menopause. SERMs are also used to treat ovulatory dysfunction and to reduce the risk of invasive breast cancer in postmenopausal women at risk or who have osteoporosis.

Selective estrogen receptor modulators work by modulating the activity of estrogen receptors, proteins in cells that are activated by estrogen. Estrogen is a hormone that has many important functions including the development of female secondary sexual characteristics, regulation of reproductive cycle, and maintenance of bone health.

Selective estrogen receptor modulators have both estrogen agonistic and antagonistic properties, depending on the type of tissue. SERMs bind to estrogen receptors and activate estrogen pathways in some tissue while blocking its effects in other types of tissue. SERMs work in the following ways:

• Estrogen-like in bone tissue, reducing bone resorption and increasing bone mineral density.
• Estrogen-like to relieve menopausal vasomotor symptoms and vaginal dryness.
• Block estrogen activity in the breast and uterus, reducing the risk of breast cancer and endometrial hyperplasia (thickening).
• Block estrogen’s negative feedback in the hypothalamus, inducing the secretion of gonadotropin-releasing hormone (GnRH). This stimulates the pituitary gland to release follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which stimulate follicle growth and ovulation.

Selective estrogen receptor modulators may also be combined with estrogen for postmenopausal women with an intact uterus, who are undergoing estrogen replacement therapy. SERMs reduce the risk of endometrial hyperplasia that can occur with estrogen therapy.

Selective estrogen receptor modulators are oral tablets approved by the FDA for use in the following conditions:

• Menopausal vasomotor symptoms (hot flashes)
• Prevention and treatment of postmenopausal osteoporosis
• Treatment of ovulatory dysfunction in women desiring pregnancy
• Vaginal dryness due to vulvar and vaginal atrophy in menopause
• Moderate to severe dyspareunia (painful sexual intercourse due to perimenopausal vaginal dryness)
• Reduction in risk of invasive breast cancer in postmenopausal women with osteoporosis
• Reduction in risk of invasive breast cancer in postmenopausal women at high risk for invasive breast cancer

Side effects of selective estrogen receptor modulators may include the following:

• Hot flashes
• Flu syndrome
• Cramps and muscle spasms
• Arthralgia (joint pain)
• Infection
• Ovarian enlargement
• Nausea
• Diarrhea
• Dyspepsia (indigestion)
• Upper abdominal pain
• Abdominal discomfort
• Gastroenteritis
• Oropharyngeal pain (oral and throat pain)
• Sinusitis (inflammation of the sinuses)
• Bronchitis (inflammation of the bronchial passage)
• Pharyngitis (throat inflammation)
• Neck pain
• Back pain
• Myalgia (muscle pain)
• Dizziness
• Insomnia
• Breast discomfort and pain
• Vaginal discharge
• Hyperhidrosis (excessive sweating)
• Deep vein thrombosis/DVT (blood clot in deep veins)
• Venous thromboembolism (block in a vein from a blood clot)
• Cerebrovascular accident
• Pulmonary embolism/PE (blood clot in the lung)
• Phlebitis (inflammation of a vein)
• Thrombophlebitis (inflammation of a vein with blood clots)
• Decreased fibrinogen (a substance produced by the liver, necessary for normal blood clotting)
• Arrhythmia (irregular heartbeat)
• Tachycardia (rapid heartbeat)
• Palpitations
• Chest pain
• Hypertension (high blood pressure)
• Dyspnea (shortness of breath)
• Edema
• Hypersensitivity reactions such as:
  • Acne
  • Generalized rash
  • Erythematous rash (rash with redness)
  • Urticaria (hives)
  • Pruritus (itching)
  • Erythema multiforme (round lesions like a bullseye)
  • Erythema nodosum (tender bumps under the skin)
  • Angioedema (swelling in the tissue under the skin or mucous membranes)
• Hypertrichosis (abnormally excessive hair growth)
• Endometrial hyperplasia
• Endometrial cancer
• Endometriosis (a disorder in which endometrial tissue is present outside the uterus)
• Ovarian cyst
• Adnexal torsion (twisting of the ovary, a complication from ovarian enlargement)
• Ovarian hemorrhage
• Tubal pregnancy
• Uterine hemorrhage
• Reduced endometrial thickness
• Fever
• Weakness
• Tinnitus
• Migraine headache
• Paresthesia (abnormal skin sensation)
• Seizure
• Stroke
• Syncope (fainting)
• Hypertriglyceridemia (high triglyceride levels in the blood)
• Increase in liver enzymes
• Leukocytosis (high white blood cell count)
• Thyroid disorder
• Hepatitis (inflammation of the liver)
• Pancreatitis (inflammation of the pancreas)
• Anxiety
• Irritability
• Mood changes
• Psychosis
• Visual disorders include:
  • Blurred vision
  • Abnormal accommodation (eye focusing)
  • Cataracts
  • Eye pain
  • Macular edema (swelling of macula, the central part of the retina)
  • Retinal thrombosis
  • Retinal hemorrhage
  • Retinal vascular spasm
  • Optic neuritis (nerve inflammation)
  • Photopsia (flashes of light in the field of vision)
  • Posterior vitreous detachment
  • Temporary or prolonged loss of vision
• Tumor growth in any organ including liver, breast, endometrium, ovary, nervous system, kidney, or bladder
• Abnormality in fetal development and congenital disorders in newborns

Information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with travel medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

Generic and brand names of selective estrogen receptor modulator drugs include:

• bazedoxifene/conjugated estrogens
• Clomid (discontinued)
• clomiphene
• Duavee
• Evista
• ospemifene
• Osphena
• raloxifene
• Serophene (discontinued)