Absence of a woman's monthly menstrual period is called amenorrhea. Secondary amenorrhea is when a woman who has been having normal menstrual cycles stops getting her periods for 6 months or longer. Causes Secondary amenorrhea can occur due to natural changes in the body. For example, the most common cause of secondary amenorrhea is pregnancy. Breastfeeding and menopause are also common, but natural, causes. Women who take birth control pills or who receive hormone shots such as Depo-Provera may not have any monthly bleeding. When they stop taking these hormones, their periods may not return for more than 6 months. You are more likely to have absent periods if you: Are obese Exercise too much and for long periods of time Have very low body fat (less than 15 to 17%) Have severe anxiety or emotional distress Lose a lot of weight suddenly (for example, from strict or extreme diets or after gastric bypass surgery) Other causes include: Brain (pituitary) tumors Drugs for cancer treatment Drugs to treat schizophrenia or psychosis Overactive thyroid gland Polycystic ovarian syndrome Reduced function of the ovaries

Inside the living body

Menstruation is a woman's monthly bleeding. When you menstruate, your body sheds the lining of the uterus (womb). Menstrual blood flows from the uterus through the small opening in the cervix and passes out of the body through the vagina. Most menstrual periods last from 3 to 5 days.

This video: Sickle cell anemia is an inherited form of anemia which is a condition in which there aren't enough healthy red blood cells to carry adequate oxygen throughout your body. Normally, your red blood cells are flexible and round, moving easily through your blood vessels. In sickle cell anemia, the red blood cells become rigid and sticky and are shaped like sickles or crescent moons. These irregularly shaped cells can get stuck in small blood vessels, which can slow or block blood flow and oxygen to parts of the body. There's no cure for most people with sickle cell anemia. However, treatments can relieve pain and help prevent further problems associated with sickle cell anemia.

The best way to prevent hepatitis A is through vaccination with the hepatitis A vaccine. Vaccination is recommended for all children age 12 months or older, for travelers to certain countries, and for people at high risk for infection with the virus. The hepatitis A vaccine is given as two shots, six months apart.

With inner ear disorders, your brain receives signals from the inner ear that aren't consistent with what your eyes and sensory nerves are receiving. Vertigo is what results as your brain works to sort out the confusion. These self-help acupressure points works with meridians to help the body regain normal healing and homeostasis.

During in vitro fertilization (IVF), eggs and sperm are brought together in a laboratory glass dish to allow the sperm to fertilize an egg. With IVF, you can use any combination of your own eggs and sperm and donor eggs and sperm. After IVF, one or more fertilized eggs are placed in the uterus .

Hearing loss can affect anyone at any age, due to heredity, medical conditions or loud noise exposure. However, as we get older, we naturally become more susceptible to hearing loss because of changes to the delicate mechanics of our ears.

Tendons are thick cords that join your muscles to your bones. When these tendons become irritated or inflamed, it is called tendinitis. This condition causes acute pain and tenderness, making it difficult to move the affected joint. Read more

Thyroid nodules are solid or fluid-filled lumps that form within your thyroid, a small gland located at the base of your neck, just above your breastbone. The great majority of thyroid nodules aren't serious and don't cause symptoms. Thyroid cancer accounts for only a small percentage of thyroid nodules. You often won't know you have a thyroid nodule until your doctor discovers it during a routine medical exam. Some thyroid nodules, however, may become large enough to be visible or make it difficult to swallow or breathe.

This tiny wireless pacemaker can be inserted into the body via a catheter instead of invasive surgery.

Uncontrolled hyperthyroidism during pregnancy can lead to serious health problems in the mother and the unborn baby. During pregnancy, mild hyperthyroidism does not require treatment. More severe hyperthyroidism is treated with antithyroid medications, which act by interfering with thyroid hormone production.

Pancreatic Auto Islet Transplantation is a procedure used to maintain insulin production and secretion in patients with chronic pancreatitis that are undergoing a total pancreatectomy, or removal of the entire pancreas. When all other medical therapies fail to control the pain, removal of the pancreas may be an option; however it can leave a person diabetic, which means that the body can no longer control blood sugar levels, and will require intensive testing of blood sugar and injections of insulin. The pancreas is an organ, located in the upper abdominal cavity, behind the stomach, liver and colon. Within the pancreas, specialized clusters of cells known as islets produce insulin, which maintain healthy blood sugar levels. The pancreas also produces enzymes to help digest food. In order to alleviate pain and maintain insulin production, the pancreas is removed from the body, processed and the islets are harvested. Once the pancreas is removed, it is placed in a solution and put into a machine where the pancreas is digested. The islets are then infused into the patient’s liver. Within a short time, the islets are expected to start producing insulin. In 80% of patients, the pain from pancreatitis is relieved by a total pancreatectomy. Over time, some patients may be diabetic and will need to take insulin to maintain healthy blood sugar levels. All patients will take pancreatic enzymes to help digest food after surgery.

What does the placenta do? The placenta is an organ that develops in your uterus during pregnancy. This structure provides oxygen and nutrients to your growing baby and removes waste products from your baby's blood. The placenta attaches to the wall of your uterus, and your baby's umbilical cord arises from it. In most pregnancies, the placenta attaches at the top or side of the uterus.

Bone is not a static part of the body — it's constantly being resorbed (broken down) and formed throughout your life. Your entire skeleton is replaced about every decade, according to the NIH. During your childhood and teenage years, bone formation occurs more quickly than bone resorption, resulting in growth. You reach your maximum bone density and strength around age 30, after which bone resorption slowly overtakes bone formation. Osteoporosis develops when there's an abnormal imbalance between bone resorption and formation — that is, resorption occurs too quickly, or formation too slowly.

Fibromyalgia syndrome (FMS) is a form of fibromyalgia where pain and stiffness occurs in muscles, tendons, and ligaments throughout the body, accompanied by other generalized symptoms such as fatigue, sleep disruption or unrefreshing sleep, mood disorder, and cognitive difficulties such as poor memory or mental ...

Cells may have slender extensions of the cell membrane to form cilia or the smaller extensions called microvilli. The microscopic microvilli effectively increase the surface area of the cell and are useful for absorption and secretion functions. A dramatic example is the human small intestine. The tissue has small fingerlike extensions called villi which are collections of cells, and those cells have many microvilli to even further increase the available surface area for the digestion process. According to Audesirk & Audesirk, this can give an effective surface area of about 250 square meters for absorption.

Recovery can take 4 to 6 months, depending on the size of the tear and other factors. You may have to wear a sling for 4 to 6 weeks after surgery. Pain is usually managed with medicines. Physical therapy can help you regain the motion and strength of your shoulder.

Nasal polyps are soft, painless, noncancerous growths on the lining of your nasal passages or sinuses. They hang down like teardrops or grapes. They result from chronic inflammation due to asthma, recurring infection, allergies, drug sensitivity or certain immune disorders.

The external jugular vein receives the greater part of the blood from the exterior of the cranium and the deep parts of the face, being formed by the junction of the posterior division of the retromandibular vein with the posterior auricular vein.