than mutations to THRB. Unlike THRB mutations, THRA mutations do not disrupt the HPT axis. This can make TR-α resistance more difficult to diagnose because patients do not typically present with elevations in thyroid hormone concentration. Due to the high TR-α1 expression in the heart, the cardiovascular system is highly affected by this condition. Additionally, thyroid hormone plays an important role in bone development. Thus, patients with this condition have consistently presented with short stature. Symptoms Symptoms of thyroid hormone resistance syndrome can be similar to those seen in hypothyroidism. Hypothyroidism is a disease in which the thyroid does not produce enough thyroid hormone. Patients with this condition have also presented with symptoms similar to hyperthyroidism. In contrast to hypothyroidism, hyperthyroidismis a disease in which the thyroid produces too much thyroid hormone. Due to the large array of potential symptoms, this condition can be misleading and is often difficult for medical professionals to diagnose. Common symptoms of TR mutation include: Depression Loss of vision Heart problems Weight gain Fatigue Hearing loss Sensitivity to cold Weakness Issues with digestion Cognitive impairment Changes to the menstrual cycle Treatment Treating patients with hypothyroidism caused by the absence of functional TRs is difficult. Treatments prescribed to patients with thyroid hormone resistance largely depend on the symptoms they present and the type of resistance they have. For those whose conditions mimic hypothyroidism, prescribing normal thyroid hormone doses may not remedy the symptoms they are experiencing. In order for a ligand to have an effect, it must be able to bind to a receptor. Individuals with a THRB or THRA mutation have less receptors that are able to bind ligand, and a corresponding drop in tissue responsiveness to thyroid hormone. For this reason, physicians may prescribe higher doses of the hormone to increase the probability that the ligand will reach a TR that is functional. Prescribing thyroid hormone in any dose to patients presenting with symptoms mimicking hyperthyroidism does not improve the condition. For these individuals, beta-blockers can be prescribed to treat the increased sympathetic activation they experience. Beta-blockers are competitive inhibitors of adrenaline, the post-ganglionic neurotransmitter released by cells of the sympathetic nervous system. By blocking the ability of receptors to bind adrenaline, beta-blockers have been observed to alleviate symptoms of anxiety, increased blood pressure, and irregular heartbeat, amongst others. Anti-anxiety medications can also be prescribed to individuals with this conditions to treat symptoms of