"I discovered it because I was really tired and not able to sleep. I went in for a routine exam and they checked it and they found out," said Ponce.
A simple blood test revealed Rachel's thyroid gland wasn't producing enough hormone, a condition called hypothyroidism. A common symptom: sensitivity to cold.
"It turns out to be a very important hormone. It affects almost every tissue in the body," said endocrinologist Dr. Ronald Stein. "It's sort of like the thermostat. It turns up the thermostat and turns down the thermostat in your body."
Other symptoms include trouble concentrating and dealing with stress.
"When someone has low thyroid condition, they're not as good in fighting stress," said Dr. Stein.
One common misconception is that low thyroid levels are to blame for weight gain. Not true, says Dr. Stein. While low thyroid levels can slow down metabolism, it's not usually the reason people can't lose weight.
Hypothyroidism can be caused by a number of factors including iodine deficiency, but those cases are rare. Experts say that it is mostly genetic.
Having a relative with a thyroid problem is a big clue. But once you're diagnosed, the solution is simple: Synthetic hormones taken in pill form.
"When I'm not on my medication I don't feel like my body is running to its optimal level of performance," said Ponce.
And with an energetic 2-year-old and another one on the way, Rachel needs to be performing at her peak.
The incidence of hypothyroidism goes up as people age. So as you get older, make sure your doctor is testing you. And one important note: Dr. Stein says once you're on a thyroid medication, stick to the same brand because different formulations can throw your body off.