Ob-Gyn questions? Ask a gynecologist online.
Hello from JustAnswer. This is Dr. Love.
Yes, having small pieces of tissue that looks like skin and passes with the menstrual period is normal. It is not actually a piece of skin. It is tissue of the lining of the uterus.
It is also true that thyroid disease can affect the menstrual period, but since the passage of tissue such as you describe is normal, there is no reason to be concerned about the possibility of thyroid disease affecting your period.
If I can provide any additional information, please let me know.
Please let me know if I can provide any further assistance.