Here are some quick tips on how to distinguish classic crystal from plain glass. 1  Hold up a glass to the light. 2  If the glass acts as a prism and you see a rainbow you are holding crystal. 3  If not, it is just plain glass. 4  When struck, crystal produces a musical ring. 5  Glass does not.
Hormonal control of menstrual cycle. The ovarian hormones circulate in the blood and are excreted in modified forms in the urine. Estimation of the urinary output by chemical methods gives an indication of the blood levels and of the total production of these substances.
1 Stress. 2  Mental stress can temporarily alter the functioning of your hypothalamus â an area of your brain that controls the hormones that regulate your menstrual cycle. 3  Ovulation and menstruation may stop as a result. 4  Regular menstrual periods usually resume after your stress decreases.