What hypothyroidism is
The thyroid, a small gland in the front of the neck, makes hormones that set the pace of your metabolism, essentially how fast or slowly your body's cells work. Hypothyroidism means the thyroid is not making enough hormone, so metabolism slows down. The most common cause in the US is Hashimoto's thyroiditis, an autoimmune condition where the immune system gradually damages the thyroid.
Symptoms, and why they are easy to miss
- Fatigue that does not improve with rest
- Unexplained weight gain, or difficulty losing weight
- Feeling cold when others are comfortable
- Dry skin and thinning hair
- Constipation
- Muscle aches and weakness
- Depressed mood or trouble concentrating
- Heavier or irregular menstrual periods
Each symptom on its own is common and nonspecific, which is exactly why hypothyroidism is often missed or blamed on stress, aging, or diet for months or years before someone checks thyroid function.
How the diagnosis actually works
A blood test for TSH (thyroid-stimulating hormone) is the standard first step. TSH is made by the pituitary gland and rises when it senses the thyroid is underperforming, so a high TSH usually means an underactive thyroid, even before symptoms are obvious. If TSH is abnormal, a clinician typically checks free T4 directly, and sometimes thyroid antibodies to confirm an autoimmune cause.
Guideline-based treatment
The standard treatment is levothyroxine, a synthetic version of the hormone the thyroid should be making, taken as a daily pill. It is inexpensive, well studied, and effective for the great majority of people. Dosing is individualized and adjusted based on repeat TSH testing, usually 6 to 8 weeks after any dose change, not based on symptoms alone, since it takes time for levels to stabilize. Guideline-based care does not include unregulated "thyroid support" supplements, glandular extracts of unclear potency, or dosing based on symptoms without lab confirmation.
Finding a doctor who treats thyroid problems
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Common questions
Can hypothyroidism cause weight gain on its own?
It can contribute a modest amount of weight gain, mostly from fluid retention and a slower metabolism, but it is rarely the sole cause of significant weight gain. Treating the thyroid corrects the thyroid-related portion; it is not a weight-loss treatment on its own.
How often should thyroid levels be rechecked once treatment is stable?
Typically once a year once your dose is stable and TSH is in the target range, or sooner if symptoms change or you become pregnant, since thyroid needs change in pregnancy.
