as you ahve not stated what kind of thyroid issue you have it is a bit hard to tell you in which direction your body will go but the answer point blankly is yes.
if you are TTC it either way it will also affect your fertility if left untreated.
left untreated thyroid issues can cause blood pressure problems (which in turn can lead onto cardiovascular and renal issues) can cause chorlesterol problems (which can lead onto heart attack and/or stroke), sight issues, nervous system problems, to name a few.
your thyroid is a key element in your bodily day to day functions, if its not working optimally and your aren't medicated for it you can cause a whole heap of issues.
i am currently fighting my GP at the moment because i have a strong family history of Hypothyroidism (under active thyorid) and my bloods keep coming back showing my thyroid id slowly slowing down but because my bloods are still 'in range' they wont medicate me even though it has been medically proven that each person is different but to have optimal thyroid function your levels need to be at the top of the range when my levels are currently in the lower half of the range. i have a long list of clinical symptoms that are common of underactive thyroid but they still wont make a medical desicion on clinical grounds (which they are meant to do)
if you can, try to get the treatment you require as you will only be setting yourself up for a whole heap of other issues later on in life.
