An open letter to endocrinology:

Dear Dr. Bow Tie,

We’re smart women without thyroids and we have tried following the “rules” of combination thyroid therapy, but everyone seems to have a different “rule”. Who should we listen to? We’ve been to our doctors (several), we’ve read Pub Med research, spent thousands of collective dollars on books, spent hours we will never get back listening to podcasts, and cruising through the Wild West of Facebook groups in search of answers to our fundamental questions. Our takeaway is that nobody knows.

If you go to the mainstream publications, nobody talks about splitting doses or when to test TSH. Is it assumed that it’s tested 24 hours after the last dose of medication the way it’s done with T4 only – the standard of practice we’ve been following for decades? If you go all the way out to the fringes you’ll hear that TSH does not matter at all and that a minimum starting dose of T3 for combination therapy is 25mcg.

Should we take our doses several times a day? All at once? The monograph for Cytomel says to take it all once a day. It seems to be written for T3 only therapy – is it the same for us? Why would patients on T3 only therapy not split a dose but patients on combination therapy take two or three doses a day?

How do we find a combination dose? Is it weight based? Do we use 3x as the basis for the strength of T3 vs T4? What if we are already on combination therapy and trying to find a good dose? Do we use weight-based dosing for our starting point? If so, how much T4 and T3 would we use? When do we change the ratio, and why? Would our FT4 and FT3 numbers prompt a change if our symptoms were unresolved?

Where does our FT4 go when we take T3? T3 dosing lowers FT4. Where is it? Is it turning into converted hormone? Are we peeing it out? Where is it? Does FT4 and FT3 matter? Where should they sit in the range? If we take T3 and it lowers FT4 below mid-range, should we be taking more T4 to bring that up again?

If the T4 dose should be lowered to add T3, wouldn’t that be putting vulnerable tissues even more at risk? Some tissues prefer converted thyroid hormone. Wouldn’t lowering the dose just subject them to even further lower levels of free T3?

When should we test TSH? If we’re taking combination therapy and splitting our doses, and testing TSH twelve hours after our last dose and it’s really low, yet we still have symptoms and signs of hypothyroidism – is the TSH right? Does it get the last say? Would it be different if we tested it 24 hours after our last T3 dose? And if so, which one is the accurate answer?

Who is finally going to define the parameters of combination therapy?