Missed Periods (Amenorrhea) Types and Causes

What is amenorrhea?

Missing a period is not an uncommon occurrence and can affect even girls and women with ‘clockwork’ menstrual cycles. To women who are sexually active, a missed period may arouse the suspicion of pregnancy. Around the 40s, a missed period may mark the onset of perimenopause. However, there a number of reasons why the periods may be delayed or a woman may miss the period altogether. The medical term for a missed period is amenorrhea but the strict definition extends beyond just the odd month without menstruation.

Types of Amenorrhea

Amenorrhea may be classified as primary or secondary. The more common type is secondary amenorrhea where a women with regular menstruation experiences a delay or totally misses a period. It is termed as secondary amenorrhea if more than 3 consecutive periods have been missed in a woman who was otherwise menstruating on a regular basis. In primary amenorrhea, a  girl or young woman has never had a period despite the presence of all the other features of puberty for more than 2 years or with the age advancing beyond 16 years.

The term amenorrhea simply means no period and it normally occurs during pregnancy, during breastfeeding and in menopause. It is not uncommon for the periods to irregular at the onset of puberty, after stopping oral contraceptives, just after pregnancy and as menopause approaches. It is also not abnormal to occasionally miss a single period or sometimes even two periods when ill, with severe psychological stress and immediately after stopping birth control. However, in these cases the period should restore shortly thereafter. If a period is missed on a regular basis though then it needs to be thoroughly investigated to identify the underlying disease.

Amenorrhea is not an indication of ovulation. Sometimes ovulation can occur as normal without menstruation following a short while thereafter. This is known as ovulatory amenorrhea. However, it is more common for ovulation not to occur and this is referred to as anovulatory amenorrhea.

Causes of Missing Periods

Since secondary amenorrhea is more common than primary, the causes focused on here are mainly for women who were having periods previously and have now missed 3 consecutive months. A severe illness particularly a systemic disease may cause secondary amenorrhea even though it may not directly involve the female reproductive tract  since the menstrual cycle is regulated by several outside structures. Women with a very low body weight, particularly those with eating disorders like anorexia nervosa, and those who are obese are more likely to experience amenorrhea. Persistent psychological stress and depression are also more likely to experience secondary amenorrhea. Another non-pathological cause that may lead to amenorrhea is excessive exercising and starvation due to extreme dieting or strict fasting.

Other conditions and diseases which may be responsible for secondary amenorrhea includes :

  • Polycystic ovarian syndrome (PCOS)
  • Hyperthyroidism or hypothyroidism
  • Premature ovarian failure
  • Narcotic drug use
  • Alcohol abuse
  • Pituitary tumors
  • Pituitary gland or hypothalamic dysfunction
  • Asherman syndrome (scarring of the uterus after surgery or infections)
  • Uterine fibroids and polyps
  • Cushing’s syndrome
  • Diabetes mellitus
  • Medication such as antidepressants, antipsychotics, chemotherapy and antihypertensive drugs.

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