When we're newly diagnosed we have no clue about how important the thyroid gland is in running our whole body, from head to toe.
Many of us wonder why our symptoms aren't relieved when first beginning thyroid hormone replacements, i.e. levothyroxine (T4) for instance that should convert to liothyronine (T3) which is the 'active' thyroid hormone needed in our millions of T3 receptor cells. The brain and heart have the most T3 receptor cells.
One of TUK's Administrators has written very helpful posts in the past and may also be informative for new members to gradually extend their knowledge.