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Thyroid Malfunction Endo, Energy and Repro 2024-2025 THYROID MALFUNCTION Jeffrey Zigman, MD, PhD, Office: Y6.214H, Phone: 8-6422 Email: [email protected] Twitter: @ZigmanLab LEARNING OBJECTIVES: After this lecture, the student shou...

Thyroid Malfunction Endo, Energy and Repro 2024-2025 THYROID MALFUNCTION Jeffrey Zigman, MD, PhD, Office: Y6.214H, Phone: 8-6422 Email: [email protected] Twitter: @ZigmanLab LEARNING OBJECTIVES: After this lecture, the student should be able to: List the common disorders resulting in hyperthyroidism/thyrotoxicosis and those resulting in hypothyroidism Distinguish among the causes of hyperthyroidism or hypothyroidism Predict how estrogen alters thyroid function tests and infer why pregnancy increases thyroid hormone supplementation requirements in hypothyroid women Recognize the mechanism of action by which thionamides function List the available drugs/therapies to manage hyperthyroidism and hypothyroidism CARDINAL SYMPTOMS OF HYPERTHYROIDISM Weight loss despite increased appetite Hand tremors Palpitations (heart racing) Heat intolerance/increased sweating Anxiety/nervousness/irritability Frequent bowel movements Fine hair Increased thirst/increased urination Light, infrequent menstrual periods Difficulty sleeping Weakness in upper arms/thighs Fatigue CARDINAL SYMPTOMS OF HYPOTHYROIDISM Fatigue, lethargy, sleepiness Cold intolerance (feeling colder than others around you) Dry skin, coarse hair, brittle fingernails Constipation Arthralgias Heavy menstrual periods Slight, if any, weight gain Hoarseness of voice Depressed mood Difficulty thinking clearly (“fuzzy” thinking) Thyroid Malfunction Endo, Energy and Repro 2024-2025 I. Hyperthyroidism - too much circulating thyroid hormone produced in the body A. “thyrotoxicosis” = high circulating thyroid hormone, irrespective of its source B. General Symptoms 1. Weight loss despite increased appetite 2. Hand tremors 3. Palpitations (heart racing) 4. Heat intolerance/increased sweating 5. Anxiety/nervousness/irritability 6. Frequent bowel movements 7. Fine hair 8. Increased thirst/increased urination 9. Light, infrequent menstrual periods 10. Difficulty sleeping 11. Weakness in upper arms/thighs 12. Fatigue C. Physical Exam Findings 1. Rapid heart rate 2. Hand tremors 3. Hyperreflexia (brisk deep tendon reflexes) 4. Possible abnormal thyroid exam (uniformly enlarged +/- thyroid bruit; one or more nodules) 5. Moist, fine skin 6. Can’t sit still 7. Lid lag +/- proptosis or other eye findings (see Graves’ Disease) 8. Onycholysis (separation of fingernail from nail bed) D. Thyroid Storm = life-threatening thyrotoxicosis 1. One of few “endocrine emergencies” 2. Rare, but associated with a high mortality rate if not treated early and aggressively 3. Suspect it if a patient has known thyrotoxicosis and begins to decompensate, especially if this occurs in conjunction with abrupt cessation of antithyroid drugs, any kind of surgical procedure, exposure to iodine-containing contrast or radioactive iodine. 4. Point scale classification system for the diagnosis of Thyroid Storm with more points given for higher body temperature, higher heart rate, signs of congestive heart failure, presence of atrial fibrillation, CNS disturbance, and gastrointestinal- hepatic dysfunction (note: you do not need to memorize this classification system, just know that it exists as a resource for you) Thyroid Malfunction Endo, Energy and Repro 2024-2025 Taken from: Hyperthyroidism and other causes of thyrotoxicosis: Management guidelines of the American Thyroid Association and the American Association of Clinical Endocrinologists. Endocrine Practice. 2011;17:456. E. Classification Systems for Hyperthyroidism 1. According to the level of dysfunction within the H-P-T axis a. Primary hyperthyroidism – due to a problem at the level of the thyroid gland itself b. Secondary Hyperthyroidism – due to a problem at the level of the pituitary leading to overproduction of TSH c. (no known instances of tertiary hyperthyroidism) 2. According to the type of process leading to the high levels of thyroid hormone a. Ongoing synthesis and release of newly made, excessive amounts of thyroid hormone b. Release of excessive amounts of pre-formed, stored thyroid hormone due to a destructive process; short-lived usually no longer than 3 months. c. Note that this classification is taken into consideration when distinguishing between the most common etiologies of hyperthyroidism (see imaging tests below) F. Disorders causing hyperthyroidism/thyrotoxicosis 1. Graves’ Disease – a. The most common cause of hyperthyroidism b. Caused by antibodies (such as thyroid stimulating immunoglobulins) that bind to and activate TSHR receptors, causing thyroid gland to grow diffusely and overproduce/oversecrete thyroid hormone (these antibodies mimic the actions of TSH, but unlike TSH, they are not under negative feedback control) Thyroid Malfunction Endo, Energy and Repro 2024-2025 c. Tends to run in families with other autoimmune conditions d. Specific physical exam findings: i. Uniformly enlarged thyroid gland/goiter +/- thyroid bruit ii. Thyroid ophthalmopathy: proptosis (bulging), stare, lid lag, redness, abnormal extraocular movements, tearing, periorbital edema i. Occurs in nearly 70% of patients if diagnosed by CT ii. Clinically evident ophthalmopathy occurs in