Fifty percent of the total mass of the atmosphere is located in the lower 5.6 km (18,000 ft) of the troposphere. It is primarily composed of nitrogen (78%) and oxygen (21%) with only small concentrations of other trace gases.
Having irregular periods is very common. I see them in my practice all the time. The causes can range from something insignificant to something that requires treatment. For example, if you're a teen, your body's hormones can fluctuate and take some time until they find a balance.
Irregular periods are common and normal during perimenopause. But other conditions can cause changes in menstrual bleeding. If any of the following situations apply to you, see a doctor to rule out other causes: 1  Your periods are very heavy, or they have blood clots.omen in perimenopause have at least some these symptoms: 1  Hot flashes. 2  Breast tenderness. 3  Worse premenstrual syndrome. 4  Lower sex drive. 5  Fatigue. 6  Irregular periods. 7  Vaginal dryness; discomfort during sex.