This is essentially the opposite of hypothyroidism, and it presents different symptoms. A hyper or overactive thyroid can “accelerate your body’s metabolism significantly,” which can lead to sudden and unexplained weight loss, notes the Mayo Clinic.
Other symptoms can occur if your thyroid is putting your bodily functions into overdrive. These include an increased (resting) heartbeat, sweating, or feeling nervous or irritable, notes the source. You may also have trouble sleeping (insomnia), or notice thinning skin or brittle hair, it adds.