Molly Sims Gained 85 Pounds During Pregnancy Due To An Undiagnosed Thyroid Issue

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Weight gain is a natural—and necessary—part of being pregnant. But model Molly Sims says she gained more than double the recommended weight during her first pregnancy, and she later discovered the issue was linked to an undiagnosed thyroid problem.

“No one tells you what’s going to happen,” she said during People’s Mom Talk video series. “I ended up gaining 85 pounds and had a bad thyroid problem that no one diagnosed throughout the whole pregnancy.”

According to the American Congress of Obstetricians and Gynecologists, women who fall into a clinically “normal” weight range should plan to gain between 25 and 35 pounds during pregnancy (the amount is higher and lower for women who are underweight and overweight, respectively). If you gain more than that, how are you supposed to know whether it’s due to a thyroid issue?

First, a primer: Your thyroid is an endocrine gland located at the front of your neck. It stores and produces hormones that, among other things, regulate your metabolism. People with an underactive thyroid, aka hypothyroidism, may require fewer calories than normal to function, which can then lead to weight gain. And people with an overactive thyroid, also called hyperthyroidism, may burn more calories than usual, which can lead to weight loss, Fatima Cody Stanford, M.D., M.P.H., an obesity medicine physician for the Massachusetts General Hospital Weight Center and professor at Harvard University, tells SELF.

If you’re gaining more weight than you expected to during pregnancy and aren’t sure if your thyroid is to blame, doctors can figure it out through the process of elimination, Stanford says, noting that a lot of excess weight gain during pregnancy is rarely due to a thyroid issue alone. In addition to thyroid hormones, hormones like ghrelin, which stimulates hunger, can be thrown out of whack during this time, she explains.

Doctors will often do a rundown of lifestyle factors like your diet, physical activity, sleep quality and duration of sleep (that can cause a “huge” shift in weight, Stanford says), and whether your circadian rhythm, i.e. the natural physical, mental, and behavioral changes you experience over a 24-hour period, has recently changed. If all those factors are the same as usual, Stanford says doctors will typically look at whether you’re taking any medications that can contribute to weight gain.

If you’re not, only then will most doctors order a blood test to check your levels of TSH, the thyroid-stimulating hormone, Stanford says, adding that they’ll also likely check your blood sugar levels for signs of pre-diabetes or diabetes.

There are a few other signs that something might be off with your thyroid, including serious fatigue, dry, brittle hair and dry, scaly skin, muscle and joint pain, a hoarse voice, and swelling in the neck, women’s health expert Jennifer Wider, M.D., tells SELF, so it’s important to mention these symptoms to your doctor if you notice them.

Luckily, there is medication to help. Having an underactive thyroid is typically treated with a drug called levothyroxine, which is similar to the hormone made by a normally-functioning thyroid gland, Wider says. If you’re pregnant, doctors will usually monitor you and adjust the dosage as needed, since pregnancy can cause hormonal shifts more than in people who aren’t pregnant, Stanford says.

But don’t automatically self-diagnose a thyroid problem if you find that you’re suddenly gaining more weight than you thought you would during pregnancy (or otherwise). “Do a deeper dive with your doctor, but don’t assume it’s any one thing,” Stanford says.

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