For how we live.
An overactive thyroid speeds the body up; an underactive one slows it down. But no single symptom is reliable — in one large screening study, individual thyroid symptoms were poor at flagging who actually had a problem.
Sea moss is sold as a 92-mineral cure-all, but no human trial shows it delivers those benefits — and because seaweed's iodine content is wildly variable, the documented risk falls on the thyroid.
"Brain fog" is a lay term for trouble concentrating and remembering, not a disease. Common drivers include poor sleep, low mood, the menopause transition, thyroid or B12 problems, and the tail of an infection.
When adults see a doctor for new fatigue, fewer than one in ten turn out to have clear physical disease. The common, treatable and often-missed exception is iron deficiency, which drains energy before it causes anaemia.
Feeling cold when others are comfortable can point to an under-active thyroid or iron-deficiency anaemia. Fingers and toes that turn white then blue in the cold are usually Raynaud's, a blood-vessel spasm.
A randomised trial and a 21-study meta-analysis found thyroid hormone normalised the blood test but left tiredness and symptom scores unchanged. A guideline now advises against routine treatment.