Synthroid and Weight Gain

Question: I have been on Synthroid for three months, just bumped up to .1 three weeks ago. Since starting the meds, I continue to gain weight–faster than before I started them. My face, hands stomach and feet are always swollen. I exercise every day (60 mins on treadmill) and eat well, drinking lots of water.
So what’s the deal? Is my thyroid in some kind of shock following treatment? Will it ever improve?

— Babs
Answer: I’m assuming your thyroid level was low when you started Synthroid. It builds up slowly over 5 weeks. Initially, it will boost your T4 and usually, secondarily, T3.
But if your initial problem was secondary hypothyroidism (i.e., TSH wasn’t significantly elevated – basically, the rheostat in the hypothalamus is set too low), when you add Synthroid (T4), the hypothalamus starts to suppress your own production of T4 to compensate. At sub-optimal doses of Synthroid, you could actually end up with less than you started with (and subsequently gain weight, develop edema).
Columbia Thyroid Clinic uses body weight in pounds to determine approximate goal dose of Synthroid in micrograms (e.g., If you weigh 150 pounds, you end up on 150 micrograms of Synthroid – same as .15 mg).

Some people do better on a combination of T4 and T3: Synthroid (T4) with either Armour (T4+T3 – available in generic, so a cheaper option) or Cytomel (T3 – more expensive). 1 grain (same as 60 mg) of Armour approximately equals .075 Synthroid; .025 mg Cytomel approximately equals .1 mg Synthroid. The goal dose is a combination of the two. For example, 150 pounds – .075 mg Synthroid + 1 grain (60 mg) Armour. Or, more commonly – 1/4 to 1/2 grain Armour and .125 to .112 of Synthroid.

So in your case, I would assume your dose is too low and you would probably do better with adding Armour and/or increasing Synthroid. If thyroid is too high, you usually have symptoms of being hot, shaky, sweaty and/or having palpitations.
When getting lab work in the morning, don’t take your a.m. thyroid that day until after blood is drawn, and be sure to get free T4 (and free T3 if taking Armour or Cytomel).

For weight loss purposes, people usually do better with their free T4 in the upper part of normal range and usually do better with some T3.