I wake up in the middle, of the night and can't fall back, asleep...is it a tyroid issue?

There are many: Different possible causes for middle ; terminal insomnia. It isn't possible with this info to tell you what the cause is. A medical evaluation (; some times sleep medicine referral) may help to identify the problem.

Possible, but unsure: What you are describing is a "maintenance insomnia." you should speak to your physician about referral got an overnight sleep study and consult with a sleep specialist.

Insomnia: Primary or secondary. Examples of secondary are mood disorders, medications, illnesses such as hyperthyroidism, or effect of illicit substances, also effect of environment.