The thyroid is a small, butterfly-shaped gland at the front of the neck. It produces hormones that regulate metabolism, energy levels, and brain function. When it stops working properly, the effects show up in places most people would not expect.
A WebMD slideshow on thyroid symptoms highlights the less obvious signs of thyroid dysfunction, both from an overactive thyroid (hyperthyroidism) and an underactive one (hypothyroidism). Many of these symptoms overlap with conditions that are common in midlife, which is part of the reason thyroid problems often go undiagnosed.
Brain Fog and Mood Changes
Hypothyroidism can slow the delivery of thyroid hormones to the brain, leading to difficulty concentrating, forgetfulness, and a general sense of mental sluggishness. This is often described as "brain fog," and it is one of the more frustrating symptoms because it can feel vague and hard to pin down.
Mood shifts are also linked to thyroid dysfunction. Depression is often an early sign of hypothyroidism, while anxiety is more commonly associated with hyperthyroidism. These symptoms are easy to attribute to stress, life circumstances, or other causes, which is one reason thyroid issues can go unrecognized for months or longer.
Period Irregularities and Pregnancy Complications
Thyroid hormones play a direct role in the menstrual cycle. Periods that are unusually light, heavy, or irregular can all point to a thyroid condition. In some cases, menstruation may stop altogether. Younger women may experience their first period earlier or later than expected.
Untreated thyroid disorders also carry risks during pregnancy. According to WebMD, complications can include preeclampsia, miscarriage, stillbirth, premature birth, and low birth weight. Thyroid screening before and during pregnancy is something worth discussing with a provider, particularly for women with a family history of thyroid issues.
Physical Changes That Are Easy to Overlook
Several physical symptoms of thyroid dysfunction tend to be dismissed as normal aging or minor issues. Facial puffiness, especially around the eyelids, lips, or tongue, can result from fluid retention caused by an underactive thyroid. Extra fluid around the eyes can also cause blurry or double vision, a condition known as thyroid eye disease.
Hair loss or noticeable thinning is another sign, particularly when thyroid dysfunction has been present for a while. Carpal tunnel syndrome, caused by fluid buildup compressing nerves near the wrist, can also be thyroid-related. Even changes in how food tastes may trace back to the thyroid's effect on taste perception and brain signaling.
Blood Pressure, Heart Rate, and Digestion
Thyroid dysfunction affects the cardiovascular and digestive systems in ways that may not immediately suggest a thyroid problem. An underactive thyroid can reduce blood vessel flexibility, raising blood pressure. An overactive thyroid can increase heart rate and also elevate blood pressure.
On the digestive side, hypothyroidism is associated with constipation, while hyperthyroidism may cause more frequent or loose bowel movements. These symptoms are common enough on their own that they rarely prompt a thyroid check unless other signs are present.
Low Libido and the Hormone Connection
Thyroid hormone imbalances can affect the production of sex hormones, which in turn can reduce sex drive. This is a symptom that many people do not connect to thyroid function, and it is rarely the first thing a provider investigates when a patient reports a drop in libido.
The connection between thyroid hormones and sex hormones is worth keeping in mind, particularly for anyone already dealing with hormonal shifts related to aging or menopause. If low libido is part of a larger pattern of symptoms, thyroid function may be one piece worth looking into.
Symptoms in Combination Are the Signal
The WebMD slideshow's takeaway is clear: thyroid disorders affect far more than metabolism. Any one of these symptoms on its own could have a different explanation. But when several show up together, especially brain fog, fatigue, mood changes, menstrual irregularities, or unexplained weight shifts, a conversation with a provider about thyroid testing is a reasonable next step.
Many of these symptoms overlap with what people experience during perimenopause, menopause, or periods of high stress. That overlap is exactly why thyroid problems can go undiagnosed. If something feels off and the usual explanations do not quite fit, asking your provider to check your thyroid is a simple step that can rule it in or out.
Source:
Surprising Signs of Thyroid Problems, WebMD, reviewed February 20, 2025. Written by Rachel Reiff Ellis, medically reviewed by Jabeen Begum, M.D.