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.
Hi fallen_angel. Thyroid disorder can cause irregular periods. Medications and stress can also be the cause. It's best to rule out pregnancy if your not totally sure and then keep a diary (I use little marks on my business diary to record my days) and call your doctor. Last edited by flourishing; 07-17-2006 at 06:36 AM.