According to WebMD, high TSH (thyroid-stimulating hormone) levels indicate an underactive thyroid gland (hypothyroidism). Common symptoms include feeling weak, tired or depressed, sensitivity to cold, constipation, brittle nails, memory problems, and heavy or irregular periods.
The Mayo Clinic notes that additional symptoms include a slowed metabolism, puffy face, unexplained weight gain, hoarseness, slowed heart rate, muscle weakness, elevated cholesterol levels, thinning hair, and swelling, pain or stiffness in the joints.
According to the Mayo Clinic, symptoms of hypothyroidism in infants include jaundice, frequent choking and a large, protruding tongue. Common symptoms seen in teenagers include delayed puberty, poor growth, delayed development of permanent teeth and poor mental development.
The Mayo Clinic states that treating high TSH levels may restore energy, reduce cholesterol and improve the pumping ability of the heart.
The standard treatment for an underactive thyroid is daily supplementation with synthetic thyroid hormone. Taking a proper dose of the oral medication consistently restores hormone levels to normal and reverses the symptoms of hypothyroidism. During the inital stages of treatment, doctors typically test TSH levels every two to three months to ensure that the right amount of thyroid hormone is being prescribed. Taking too much thyroid hormone can result in hyperthyroidism and cause symptoms such as insomnia, heart palpitations, shakiness and increased appetite, according to the Mayo Clinic.