It's normal to lose about 50 to 100 hairs every day, says the American Academy of Dermatology (AAD). It's usually not a big deal, because about the same number of hairs grow back to replace them.But if they don't grow back, it's most likely the result of hereditary hair loss -- a condition that the AAD says affects about 80 million men and women.

Hair loss may also be a shared symptom of other medical conditions in the body. Among them are:

1 Thyroid dysfunction - Although an underactive thyroid is most commonly associated with hair loss, an overactive thyroid also can have the same effect, Dr. Ferraro says. Because the thyroid is responsible for the body's metabolism, underactivity can result in weight gain, dry skin and constipation along with reduced hair growth. An overactive thyroid can result in weight loss, a rapid heartbeat or diarrhea. “The condition can also take a toll on a person's hair,” Dr. Ferraro says. “Your doctor can test your thyroid and treat the condition.”

2 Iron deficiency anemia occurs with blood loss. It can be checked with blood tests, such as a complete blood count and iron stores. Along with hair loss, symptoms can include fatigue and feeling cold.

3Polycystic ovarian syndrome is a condition in which the ovaries produce too much male hormone.

4. Systemic lupus erythematosus is an autoimmune disorder in which the body attacks normal tissue. Dr. Ferraro says lupus can present many symptoms besides hair loss, including joint aches, rashes and fatigue. It can be diagnosed with a blood test for antibodies and treated by a rheumatologist.

5 Heart disease. “Some studies are showing there may be a relationship between male pattern baldness at the crown of the head and heart Disease . This may be explained by loss of circulation or possibly by increased levels of testosterone that are linked to heart disease. The risk of heart disease for men with high cholesterol and severe baldness may be as much as three times greater than the risk of men with high cholesterol and no baldness.

Read more - https://www.uhhospitals.org/blog/articles/2018/04/your-hair-and-your-health