The follicular phase begins with an increase in follicle-stimulation hormone (FSH), which causes increases in luteinizing hormone (LH) and gonadotropin-releasing hormone (GnRH). Concurrent increases in estrogen levels cause increases in progesterone, stimulating proliferation of the endometrium.
Examples of insulators include plastics, Styrofoam, paper, rubber, glass and dry air. The division of materials into the categories of conductors and insulators is a somewhat artificial division. It is more appropriate to think of materials as being placed somewhere along a continuum.
Some materials hold their electrons very closely, not allowing the electrons to move through them well. These materials are known as insulators. Materials that do allow their electrons to move through them easily are called conductors. Cloth is a good insulator, while metals generally are good conductors.