Causes of low thyroid and dizziness include autoimmune diseases, pregnancy, certain medications, insufficient iodine levels and thyroid destruction during surgical removal of tumors of the thyroid gland, according to Mayo Clinic. Low thyroid and dizziness can also result from damage to the pituitary gland by tumors, stroke or trauma.
Damage to the pituitary gland results in failure of the organ to signal to the thyroid how much hormone to produce. The thyroid fails to produce any hormones, leading to dizziness, low blood pressure, decreased heart rate and lethargy, notes MedicineNet. Some women develop low thyroid and experience dizziness during pregnancy due to the production of antibodies against their thyroid glands. The condition can lead to miscarriage or premature delivery due to the increase in high blood pressure, reports Mayo Clinic.