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.
So, it is not too bad idea to know what are the most common causes of irregular period, and below are some of these causes: 1  Stress (bad emotional level) and illness. 2  A significant weight change of your body (being in not ideal weight, either too thin or obesity). 3  The infections in the pelvic organs.