Using TSH as the Sole Marker of Thyroid Function
In conventional medicine, it is considered standard of care to run a screening thyroid stimulating hormone (TSH) test before ordering any other thyroid lab tests. TSH is a hormone released by the pituitary gland that signals the thyroid to make more thyroid hormone. If everything is working properly, the body balances TSH levels with an inherent negative feedback mechanism to decrease TSH when circulating thyroid hormone is high, and to increase TSH when circulating thyroid hormone is low. But there are three major issues with relying on TSH as the SOLE parameter:
The range for “normal” TSH of 0.5-5.0 is misleading and is the main reason for the epidemic of under-diagnosed thyroid conditions. Many individuals will find themselves right in the middle of that range around 3, yet feeling miserable and left with no answer as to why. Not only do these broad reference ranges leave many people in misery, but they also allow thyroid disorders to silently progress until they become “bad enough” to treat! For this reason, many thyroid specialists have developed their own functional ranges to detect a system that isn’t functioning optimally in order to initiate supportive measurements to hopefully alleviate symptoms and stop the progression to a more serious thyroid condition.
When it comes to fertility, this becomes even more of an issue, as a TSH above 2.5 has been associated with an increased risk of miscarriage and other pregnancy complications.
TSH should reflect the level of actual circulating thyroid hormone, but in some cases, our internal feedback mechanisms can be a little off! This happens most often when the issue is arising at the level of the hypothalamus or pituitary, where thyroid releasing hormone (TRH) and TSH are produced, respectively. There are a number of reasons for hypothalamic and pituitary dysfunction, including, but not limited to: a traumatic brain injury, severe blood loss during childbirth, past or present eating disorders, PTSD, and even significant chronic stress!
Running TSH only gives us ONE piece of a very complex puzzle. Thyroid issues can arise from a number of areas. It is not only important to get a full thyroid picture for proper detection, but it is also crucial for proper treatment! Thyroid replacement is not the only treatment that should be initiated with a thyroid condition, and it is important to know where the pathway went awry, so further work can go into detecting and addressing the root cause.