Thyroid Function: What It Does, How It Goes Wrong, and What to Watch For

When your thyroid function, a gland in your neck that produces hormones regulating metabolism, energy, and body temperature. Also known as thyroid gland activity, it quietly controls how fast your body uses energy, how you feel, and even how your heart beats. If it’s underactive, you might feel tired all the time, gain weight without reason, or get cold easily. If it’s overactive, you could feel jittery, lose weight without trying, or have a racing heart. These aren’t just "feelings"—they’re signs your thyroid isn’t working right.

Thyroid hormones—T3 and T4—don’t work alone. They’re guided by TSH, thyroid-stimulating hormone made by the pituitary gland that tells the thyroid how much to produce. When TSH is high, your thyroid isn’t making enough. When it’s low, your thyroid might be overproducing. That’s why a simple blood test for TSH is often the first step. But it’s not the whole story. Some people have normal TSH but still feel awful because their body isn’t converting T4 to active T3 properly. Others have antibodies attacking their thyroid—this is Hashimoto’s disease, an autoimmune condition where the immune system mistakenly destroys thyroid tissue, the most common cause of hypothyroidism in the U.S.

Medications like levothyroxine help replace what your thyroid can’t make, but they’re not one-size-fits-all. Some people need higher doses, others struggle with side effects like heart palpitations or insomnia. And it’s not just about pills. Certain drugs—like lithium, amiodarone, or even some antidepressants—can mess with thyroid function. Even too much iodine, from supplements or seaweed, can throw things off. That’s why checking your meds and diet matters as much as your lab results.

You’ll find posts here that cut through the noise. One explains how thyroid function connects to weight loss struggles, even when you’re eating right and exercising. Another breaks down why some people feel worse on thyroid meds—not because they’re not working, but because something else is missing. There’s a guide on spotting the difference between a thyroid issue and just being burned out. And another shows how certain antibiotics and diuretics can indirectly affect your thyroid, even if they’re not meant to.

This isn’t about guessing. It’s about knowing what your body’s telling you—and what tests actually mean. Whether you’ve been diagnosed or just feel off and can’t figure out why, the posts below give you real, no-fluff info on what’s happening inside and what to do next.