Sub clinical hypothyroidism
Many of us here have low thyroid functioning. As long as you take medication (Synthroid is the most common), it isn't an issue. Even if your thyroid functioning is just a bit low (you didn't specify what your levels were), it may not affect your weight even without medication (but because of the complexity of the human body, the levels need to be adjusted regardless of any effect on weight or not).
Lora
14 years out; 190 pounds lost, 165 pound loss maintained
You don't drown by falling in the water. You drown by staying there.
If what he means is what I think it does, it's not a huge deal. Basically your thyroid is a little less productive than desirable, but not enough to give you symptoms.
At least, that's what I have. My TSH runs a bit higher than ideal without medication, but I've never had any of the symptoms of hypothroidism. A tiny daily dose of Sythroid or Armour Thyroid and mine is back in the "good" range and I don't notice any difference at all. Some people are very sensitive to thyroid hormones, though, so you may find you feel better with a little supplementation. It may take a little fine tuning to get the dosage right, but it isn't anything to freak out about.
I think it has as much to do with aging and being female than anything else. Also, doctors are getting more aggressive about treating borderline levels than they used to be. It used to be a TSH of 4 or even a little higher was considered fine, but most doctors I've talked to in recent years want it to be around 2.