Just wondering if any other people have experienced anything similar to this. I am 19 years old. My last period started on January 1, 2019. I have irregular cycles anyway, but my longest cycle before this was 54 days. Normally they are from 40-48 days. Since my cycles are so long, I didn't start taking pregnancy tests until April. Every test came back negative. No typical pregnancy symptoms, except one day I remember having what I can only describe as a spell. I had a headache that lasted for hours and was so bad that I was sensitive to light. On May 9, I finally went to the doctor. They of course gave me another test, which came back negative. The doctor decided to have lab work done. They tested my thyroid, my prolactin levels, and my cholesterol. My prolactin was at 17.1 (within normal range for non-pregnant women). However, my cholesterol was 222 (supposed to be 200), and my TSH levels were at 6.68 (normal is from 0.3-4). A higher number indicates an underactive thyroid. However, my T4 levels were normal. This is a condition known as subclinical hypothyroidism. While the doctor informed me that this is enough to cause absent periods, I have never heard of this happening before. I know that full blown hypothyroidism could definitely affect your period, but I guess it is hard for me to believe that subclinical hypothyroidism could cause me to lose my period completely, since my levels are not much higher than normal. Has anyone else experienced this or does anyone have any thoughts?