Hyperthyroidism (overactive thyroid) is a condition in which your thyroid gland produces too much of the hormone thyroxine. Hyperthyroidism can accelerate your body’s metabolism significantly, causing sudden weight loss, a rapid or irregular heartbeat, sweating, and nervousness or irritability. It can also cause a wide variety of signs and symptoms, including:
- Sudden weight loss, even when your appetite and the amount and type of food you eat remain the same or even increase
- Rapid heartbeat (tachycardia) – commonly more than 100 beats a minute – irregular heartbeat (arrhythmia) or pounding of your heart (palpitations)
- Increased appetite
- Nervousness, anxiety and irritability
- Tremor — usually a fine trembling in your hands and fingers
- Sweating
- Changes in menstrual patterns
- Increased sensitivity to heat
- Changes in bowel patterns, especially more frequent bowel movements
- An enlarged thyroid gland (goiter), which may appear as a swelling at the base of your neck
- Fatigue, muscle weakness
- Difficulty sleeping
- Skin thinning
- Fine, brittle hair
A variety of conditions can cause hyperthyroidism. Graves’ disease, an autoimmune disorder, is the most common cause of hyperthyroidism. It causes antibodies to stimulate the thyroid to secrete too much hormone. Graves’ disease occurs more often in women than in men. It tends to run in families, which suggests a genetic link. You should tell your doctor if your relatives have had the condition. Other causes of hyperthyroidism include:
- excess iodine, a key ingredient in T4 and T3
- thyroiditis, or inflammation of the thyroid, which causes T4 and T3 to leak out of the gland
- tumors of the ovaries or testes
- benign tumors of the thyroid or pituitary gland
- large amounts of tetraiodothyronine taken through dietary supplements or medication
During pregnancy, the hormone HCG (human chorionic gonadotropin) is produced. HCG is the hormone that “pregnancy tests” detect. HCG increases to a peak at around 12 weeks. It has mild thyroid stimulating effects and, as a result, can cause some symptoms of hyperthyroidism. HCG is in part responsible for the nausea during the first trimester. In situations of multiple pregnancies (twins, triplets) HCG levels are even higher, and symptoms can be more pronounced. Temporary subclinical (no apparent symptoms) hyperthyroidism occurs in 10-20% of normal pregnant women during this period, and these women typically do not require treatment. Pregnancies complicated by uncontrolled hyperthyroidism may result in higher incidences of:
- Spontaneous abortion (miscarriage)
- Preterm labor
- Low birth-weight babies
- Stillbirths
- Complications of pregnancy, including pre-eclampsia (a condition associated with hypertension, low blood platelet count, protein in the urine and mental changes) and heart failure.
References:
https://www.mayoclinic.org/diseases-conditions/hyperthyroidism/symptoms-causes/syc-20373659
https://www.healthline.com/health/hyperthyroidism#causes
https://www.medicinenet.com/hyperthyroidism_and_pregnancy/views.htm
