Thanks for your responses guys! I’ve found this;
http://www.lifestyleintegration.com.au/learning-centre/blog/123-is-bad-posture-stealing-your-health.html
A quote referring to the thyroid;
Let’s use an example to understand the implications of this. Suppose someone has an under active thyroid. There are many reasons for this and one of the potential ones is bad posture. This is possible as the nerves that supply the thyroid come from the lower neck (C7). If a person has been working a desk job for a long time as an example and now suffers from poor posture and a head that is no longer stacked vertically over their body there will be constant pressure on this nerve to the thyroid. If this goes on long enough wear and tear (osteoarthritis) to the lower neck will occur. In this example we would now have constant pressure on the nerve that would be interfering with the messages to the thyroid resulting in decreased function.