Snapshot A 40-year-old woman presents to her primary care physician with complaints of increased fatigue and a 10-lb weight gain over the last 2 months. She states that she "feels cold" all the time, has decreased energy, and is experiencing worsening constipation. On physical exam, her pulse is 45/minute, her skin is dry and cold, and her lateral eyebrows are thinned. She also has delayed deep tendon reflexes. Introduction Inadequate thyroid hormone in tissues Most commonly caused by Hashimoto's thyroiditis Less common causes include subacute or postpartum thyroiditis iatrogenic causes (inadequate replacement after surgical ablation) drugs (iodide, amiodarone, sulfonamides, lithium) pituitary dysfunction Myxedema refers to hypothyroidism with mucopolysaccharides deposits in the dermis Subclinical hypothyroidism clinical entity with elevated TSH but normal T3/T4 values does not require treatment unless presence of anti-TPO antibodies clinical symptoms of hypothyroidism hyperlipidemia menstrual dysfunction Presentation Symptoms weakness and fatigue cold intolerance constipation weight gain depression menstrual irregularities galactorrhea thyrotropin-releasing hormone can stimulate prolactin secretion hoarseness myopathy Physical exam dry, cold skin edema with puffy face, eyelids, and hands (myxedema) skin thinning of lateral eye brows bradycardia delayed relaxation of the deep tendon reflexes Evaluation Labs elevated TSH is most sensitive measure decreased serum and free T4 may have megaloblastic anemia Scan shows < 10% radionucleotide uptake Differential Diagnosis Anxiety, neurosis, mania, pheochromocytoma, chronic alcoholism, myopathy, myasthenia gravis, dental disease Hashimoto's Disease Autoimmune lymphocytic infiltration of thyroid gland Usually in females age 30-50 8:1 female to male ratio Diagnosis confirmed by antithyroid peroxidase (TPO) antibodies Early in disease, patients may have normal TSH and normal free T4 Treat with lifelong levothyroxine (a thyroid hormone replacement) importantly the dose must be increased during pregnancy Subacute Thyroiditis Seen following flu-like illness with soar throat and fevers Presents with jaw / tooth pain Initially looks like hyperthyroidism as gland spills T4 Later converts to hypothyroidism Treatment aspirin cortisol for severe disease Usually self-limiting and resolves in weeks to months Resistance to Thyroid Hormone (RTH) Syndrome characterized by reduced end-organ responsiveness to thyroid hormone Caused by mutations in the TH receptor (TR) beta gene Diagnosis is based on persistent elevations of serum free T(4) and T(3) levels in the absence of TSH suppression Features in children: failure to thrive, growth retardation, ADHD Features in adults: goitre, thyrotoxic cardiac symptoms Myxedema coma The only emergent hypothyroid condition Precipitated by cold exposure infection analgesics drugs spontaneous Presentation stupor coma seizures hypotension hypoventilation Treatment IV levothyroxine hydrocortisone mechanical ventilation