Perimenopause — the hormonal transition leading up to menopause, which can last for years and sometimes more than a decade — has become one of the hottest topics on social media, with women flocking to TikTok and Instagram to compare symptoms, swap advice and joke about “cougar puberty.”
But while weight gain, fatigue, mood swings and brain fog are often blamed on fluctuating hormones, they may also be signs of an underlying thyroid imbalance, warns functional medicine practitioner and thyroid specialist Dr. Amie Hornaman, author of ‘The Thyroid Fix.’
Hornaman knows firsthand what an underactive thyroid can do to the body. When she was in her 30s, she suddenly gained 40 pounds despite being a fitness competitor who exercised intensely and followed a strict diet. She struggled with a host of other unexplained symptoms, yet six doctors told her she was “normal” before she was finally diagnosed with Hashimoto’s disease, an autoimmune disorder that damages the thyroid gland and is the leading cause of hypothyroidism, or underactive thyroid. The frustrating journey ultimately inspired her to focus her career on thyroid health.
“The thyroid is the master gland,” Hornaman tells us. “From head to toe, it runs the show. It ultimately controls hormonal balance, it controls whether we go into perimenopause and menopause early, and how we feel once we’re in that stage. It even controls how well hormone replacement therapy will work.”
“When hormones start to decline in our 30s and 40s, that can be enough to turn on the autoimmune switch for Hashimoto’s disease,” she explains. “Women will say, ‘I’m gaining weight, I have no energy, no libido,’ and blame it on perimenopause and menopause. Yes, declining hormones can cause those symptoms, but low thyroid function can be part of the picture too.”
Because hormonal fluctuations at midlife may trigger thyroid problems, she urges women suffering with unexplained symptoms to evaluate both their hormone levels and their thyroid function, rather than focusing on just one or the other.
“Test, don’t guess,” she advises. In her book, she lists the six thyroid markers that anyone experiencing persistent symptoms should ask for. While many conventional doctors rely on just one — the TSH, or thyroid-stimulating hormone, test — rather than digging deeper for the full picture.
Hornaman says if your doctor balks at ordering the extra tests, you owe it to yourself to find a new doctor.
She is also critical of the way many thyroid test results are interpreted.
“Normal is a setting on a dryer,” she says. “It should never be used to describe health or labs.”
Instead, she believes everyone should focus on achieving optimal thyroid function rather than simply falling within a laboratory’s normal range.
One area of ongoing debate is the interpretation of thyroid-stimulating hormone levels. While many laboratories consider a TSH range of roughly 0.4 to 4.5 mIU/L to be normal, some functional and integrative practitioners argue that the range is too broad and may not accurately reflect optimal thyroid health for every individual.
That philosophy extends to thyroid medication as well. Hornaman notes that Synthroid (levothyroxine), a T4-only medication, is the second most-prescribed drug in the United States.
“The majority of people diagnosed with hypothyroidism are put on T4, Synthroid or levothyroxine,” she says. “Only 2% of people with hypothyroidism need only T4. Ninety-eight percent need a T3 and T4 blend. If you are on T4 only, you are not going to be optimized.”
According to Hornaman, the biggest warning signs of thyroid dysfunction are weight gain or an inability to lose weight, hair thinning or hair loss, and persistent fatigue.
“When those start stacking together, those are pretty big warning signs,” she says.
Additional symptoms can include brain fog, anxiety, depression, insomnia and constipation.
“Whenever you think of low thyroid, think low and slow,” she says. “Low moods, slow metabolism, slow brain function.”
Hornaman also highlights T2, a lesser-known hormone derivative of T3 that is available as a dietary supplement.
“It has over 30 years of research on it. I call it the forgotten thyroid hormone because it is so powerful when it comes to metabolism and inflammation. It will increase our baseline metabolism, decrease inflammation, improve fatty liver, improve insulin sensitivity, making us more insulin sensitive instead of insulin resistant. It helps the thyroid convert inactive thyroid hormone to the active version and has a huge impact on how we feel,” she says.
Because it’s not available in pharmaceutical form, there is currently no widely available clinical test for T2 levels, but she notes it’s safe to take, even alongside other thyroid medications.
Above all, Hornaman wants women to trust themselves.
“Never accept a diagnosis of normal if you don’t feel normal,” she says. “You know your body.”