Amenorrhea is defined as delay of menstruation. There are 2 types of amenrrhea:
Primary amenorrhea is defined as no period by age 16 and
Secondary amenrrhea is defined as period beginning at the appropriate age, but later stops for more than 3 cycles or 6 months.
Women who have a delay of period used to think that may be pregnant. In fact, there are many reasons of amenorrhea. In this article, we will discuss causes and symptoms of primary amenorrhea.

I. Causes
1) Delay due to purity characteristic
Some women may just start to have breast tender at age 16 due to nutritional deficiency or genetic passing through form generation to generation causing delay of menstruation.

2) Defects of reproductive system
a) Androgen insensitivity syndrome
The person develops the appearance of a female despite having a male chromosomal pattern and gonadal production of male hormones. However, the person does not have a uterus or periods, pubic and axillary hair are scant, and testosterone levels are high in the male hormone range.

b) Turner syndrome
A common genetic condition that one of the X chromosomes is missing,resulting in absent menses and failure to develop ovaries.

c) Policystic ovarian syndrome
In some women, the uterus develops but the vagina does not, or a setum blocking release of the menstrual blood causing pelvic pain at regular intervals similar to the expected pattern of menstrual periods.

3) Hymen problem (lack of an opening in the membrane at the entrance of the vagina)
Hymen is a membrane that surrounds or partially covers the external vaginal opening. If the membrane is too thick causing puberty, menstrual blood becomes trapped behind resulting in painful pelvis and amenorrhea if the collection of blood may become larger with each month period. Hymenotomy may also be required if the hymen is particularly thick.

4) Problem with the hypothalamus or pituitary gland
As we know, in order to start a menstrual cycle, the hypothalamus releases hormones that stimulates the pituitary gland to release follicle-stimulating hormones and luteinizing hormones. If any steps go wrong, there is no egg being produced by the follicle causing amenorrhea.

5) Drastic weight loss or obesity
Females who are obese often experience amenorrhea as a result of excess fat cells causing hormone imbalance that interfere with the process of ovulation.

6) Eating disorder
Females with anorexia nervosa or bulimia nervosa often experience amenorrhea as a result of maintaining a body weight that would be too low to sustain a menstrual cycle.

7) Imbalanced diet
Imbalanced diet causes deficiency of certain nutrients and minerals, such as magnesium deficiency resulting in imbalance of estrogen and progesterone that interferes with normal processing of the menstrual cycle.

8) Thyroid diseases
Hyperthyroidism occurs when the thyroid releases too many of its hormones causing hormone imbalance resulting in too much thyroid hormone in the bloodstream and over activity of the body’s metabolism causing the absence of menstrual cycles. The most common cause of hypothyroidism is Hashimoto’s thyroiditis, a disease of the thyroid gland where the body’s immune system attacks the gland causing failure of the pituitary gland to secrete a hormone to stimulate the production of hormones that needs to regulate the stage of the menstrual cycle.

II. Symptoms
a) Dry vagina
b) Headache
c) Increased hair growth in a male pattern
d) Voice changes
e) Breast size changes

I hope this information will help. If you need more information, please follow my article series of the above subject at my home page at:
http://medicaladvisorjournals.blogspot.com
http://menstrualcycleii.blogspot.com/