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.
- Nikeyah*. It's normal to have irregular periods for the first few years of menstruating. Several things can cause irregular periods, including changing levels of hormones. Doctors sometimes prescribe birth control pills to regulate periods since they can help control hormone levels. Birth control pills can have some side effects, like nausea, possible weight gain, headaches, mood changes, breast tenderness, and blood clots.