Thyroid Disorders: Causes, Symptoms & Treatment - PDF

Thyroid Disorders  Prevalence & Impact of Thyroid Disease More than 12% of the U.S. population will develop a thyroid condition during their lifetime. 20 million Americans have some form of thyroid disease Women are five to eight times more likely than men to have thyroid pr...

Thyroid Disorders  Prevalence & Impact of Thyroid Disease More than 12% of the U.S. population will develop a thyroid condition during their lifetime. 20 million Americans have some form of thyroid disease Women are five to eight times more likely than men to have thyroid problems One woman in eight will develop a thyroid disorder during their lifetime Prevalence increases with age and more common in adults>65years  Physiologic Effects Promote basal metabolic function, regulate O2 consumption, and heat production Affect cardiovascular muscle contraction Stimulate bone resorption and bone formation Permit normal glucose metabolism, absorption and storage Function in the synthesis and breakdown of lipids Affect the rates of metabolism of many hormones and drugs.  Hypothalamic-Pituitary-Thyroid Axis Low serum levels of thyroid hormones T3 and T4 trigger Thyrotropin Releasing Hormone (TRH) release from the hypothalamus, which in turn causes Thyroid Stimulating Hormone (TSH) release from the pituitary. TSH causes increased release of thyroid hormones until a normal serum level is reached.  HYPOTHYROIDISM Hypothyroidism is a condition resulting from the synthesis of thyroid hormone that is insufficient to meet the body’s needs. Most common disorder of the thyroid gland. Primary Hypothyroidism occurs when diseases or treatments destroy thyroid tissue or interfere with thyroid hormone biosynthesis Secondary Hypothyroidism is caused by disorders of the pituitary gland or hypothalamus. Subclinical hypothyroidism is an asymptomatic condition in which a patient has an elevated serum thyroid-stimulating hormone (TSH) level but a normal thyroxine (T4) level.  Hypothyroidism Common causes Chronic autoimmune (Hashimoto) thyroiditis, surgical removal of the thyroid, and radiation treatment. Medicines such as amiodarone, lithium, interferon alpha, and interleukin-2 Risk factors for an elevated TSH level Female sex Pituitary or hypothalamic disease Advancing age White race Type 1 diabetes Down syndrome Family history of thyroid disease Goiter Previous hyperthyroidism (ablation therapy leading to iatrogenic thyroid dysfunction) External-beam radiation in the head and neck area.  Hypothyroidism – Classic Presentation Cold intolerance Weight gain Menstrual abnormalities Constipation Forgetfulness Depression Fatigue Image received November 3 rd, 2020, from https://cookwithkathy.wordpress.com/tag/hypothyroidism/ (Benenson et al., 2019)  Hypothyroidism – Physical Examination Delayed deep tendon reflexes Coarse dry skin Brittle nails Hair loss Goiter Bradycardia Hoarseness  Hypothyroidism – Differential Diagnoses Depression Chronic Nephritis Chronic Fatigue Syndrome Goiter Congestive Heart Failure Hypopituitarism Pituitary tumor Addison’s disease  Diagnostic Tests Primary/main test=TSH level in a blood sample Normal level of TSH =0.4 -4 mlU/L Changes in TSH can serve as an “early warning system” – often happening before the actual level of thyroid hormones in the body becomes too high or too low. A high TSH level indicates that the thyroid gland is not producing enough thyroid hormone (primary hypothyroidism). (Thyroid Function Tests, 2020)  T4 Tests T4 is the main form of thyroid hormone circulating in the blood. Most of the T4 in the blood is attached to a protein called thyroxine-binding globulin. A Total T4 measures the bound and free hormone. The “bound” T4 can’t get into body cells. A Free T4 measures what is not bound and able to enter and affect the body tissues. Tests measuring free T4 – either a free T4 (FT4) or free T4 index (FTI) precisely reflect how the thyroid gland is functioning when checked with a TSH. Normal level of Free T4 = 0.8 to 1.8 ng/dL Elevated TSH and low FT4 or FTI indicates primary hypothyroidism due to disease in the thyroid gland. Diagnostic Tests Labs Lipid profile – hyperlipidemia CBC - anemia ECG - bradycardia Imaging test – usually not necessary unless there’s a nodule Lab findings Condition TSH Free T4 T3 Other Thyroid labs Normal normal normal Normal negative Primary High Low Hypothyroid Subclinical High Normal Hypothyroid Hashimotos High Low Present antibodies (TPO)  Hypothyroidism Treatment PHARMACOLOGIC Levothyroxine sodium (synthetic thyroxine, T4) [Synthroid, Levoxyl] Young, healthy, non-pregnant adults  1.6 mcg/kg PO daily Adults > 50-60 yrs or with CHD  25 to 50 mcg PO daily Adults > 50-60 yrs and with CHD  12.5 to 25 mcg PO daily NON-PHARMACOLOGIC/EDUCATION Educate about need for lifelong therapy Monitor for adverse effects, which may mimic s/s of hyperthyroidism Patients should take medication on empty stomach (30-60 mins before breakfast or 2- 4 hours after last meal) Certain medications can interfere with absorption (ex. estrogen therapy, antacids, iron) FOLLOW UP Monitor serum TSH 4-8 weeks after initiation of therapy or after dosage adjustments Periodic TSH measurements at 6 months & then 12 month intervals, unless symptomatic (Garber et al., 2012; Hollier, 2018; Buttaro et al.,  Myxedema Coma - decompensated, severe form of hypothyroidism Condition of severe, life-threatening, and decompensated hypothyroidism in which thyroid hormone levels are dangerously low. Common in elderly women with long-standing preexisting hypothyroidism. Triggers may include cold temperature (more common during winter months) precipitating comorbidities, such as infection, stroke, and heart failure or the use of sedative, analgesic, antidepressant, hypnotic, antipsychotic, or anesthetic medications. Patients with preexisting hypothyroidism may also present with myxedema coma following a period of prolonged noncompliance with thyroid hormone replacement. Signs and symptoms are exacerbations of the typical manifestations of hypothyroidism and may include extreme lethargy, which can progress to stupor or coma, hypothermia, respiratory depression, bradycardia, hyponatremia, and renal impairment. Management of myxedema coma should be considered as promptly as possible, given the increased mortality of the disease (25%–60% despite treatment), and can be started even before laboratory results demonstrating abnormal serum TSH and T4 concentrations. The treatment of myxedema coma should be in an intensive care unit (ICU) setting.  Hyperthyroidism Clinical state that results when the body’s tissue are exposed to an increased level of circulating thyroid hormone. The prevalence of hyperthyroidism is approximately 5-10 times less than hypothyroidism. White and Hispanic populations in the U.S. have a slightly higher prevalence of hyperthyroidism in comparison with black populations. Women>men 7:1 Age at diagnosis predominantly 20-40 years. “Overt" hyperthyroidism does not require the presence of symptoms or nonspecific symptoms with low or undetectable TSH level and an elevated T4 or T3 level. Subclinical hyperthyroidism is an asymptomatic condition in which a patient has a low serum TSH level but normal T4 and triiodothyronine (T3) levels.  Hyperthyroidism Common causes Graves disease functional thyroid nodules toxic multinodular goiter toxic adenoma Risk factors for a low TSH level female sex advancing age black race low iodine intake personal or family history of thyroid disease ingestion of iodine-containing drugs, such as amiodarone.  Hyperthyroidism – Classic Presentation Adrenergic symptoms, hypermetabolism Heat intolerance Palpitations Tremor Nervousness Insomnia Weight loss despite increased appetite Hyperdefecation Menstrual Abnormalities Image received November 3 rd, 2020, from https://tr-i-life.tumblr.com/post/32017595712/hyperthyroidism- mnemonic (Benenson et l., 2019)  Hyperthyroidism – Physical Exam Warm moist skin Lid lag Brisk deep tendon reflexes Tachycardia Stare [an appearance of a fixed look due to retraction of eyelids] Neuromuscular symptoms such as weakness of proximal muscles. Psychiatric symptoms which vary from anxiety to frank psychosis. (Gupta, 2018) Long-standing untreated hyperthyroidism may develop atrial fibrillation (10% to 15% of patients) or heart failure (5.8% of patients) Graves orbitopathy (exophthalmos or periorbital edema) Photophobia, excessive lacrimation, increased eye sensitivity to wind or smoke, or a sensation of a foreign body in the eyes. In severe cases, blurred vision, diplopia, or reduced color perception may form. Hyperthyroidism – Differential Diagnoses Anxiety Arrhythmias Diabetes Mellitus Malignancy Pheochromocytoma Depression Menopause Panic disorder Diagnostic Tests TSH: Low TSH level indicates that the thyroid is producing too much thyroid hormone (hyperthyroidism). Free T4 - elevated T3 - helpful to diagnose hyperthyroidism or to establish the severity of the hyperthyroidism. Normal Serum Total T3 = 75 to 195 ng/dL (1.1 to 3 nmol/L); though ranges may vary between laboratories. FREE T3 - Measurement of free T3 is doable but is often not dependable and therefore not typically useful TSI (thyroid stimulating immunoglobulin) – elevated in Graves disease Lab Findings Condition TSH Free T4 T3 Other thyroid labs Primary Low High High TSI elevated Hyperthyroid in Graves Subclinical Low Normal Normal Hyperthyroid  Diagnostic Tests Other Labs: Liver Profile – elevate alk phos, ALT, AST, total bilirubin CBC - ESR elevation Ultrasound – to evaluate goiter, nodule Radioiodine Uptake Scan – elevated uptake in Graves Disease, toxic nodule EKG – tachycardia, afib  Hyperthyroidism Treatment PHARMACOLOGIC Beta-blockers  to reduce symptoms associated with hyperthyroidism Propanolol 10-40 mg PO 3-4 times per day Atenolol 25-100 mg PO 1-2 times per day *Caution in patients with asthma or CHF Antithyroid drugs (thionamides)  to decrease thyroid hormone synthesis 1st line: Methimazole (Tapazole) initial 10-30 mg PO daily; maintenance 5-10 mg PO daily. Propylthiouracil (PTU) 50-100 mg PO TID… Should ONLY be used in 1 st trimester of pregnancy! *Baseline CBC & LFTs prior to initiation of therapy; Monitor for rare, serious side effects of agranulocytosis & hepatotoxicity. MANAGEMENT Referral Radioactive iodine therapy Surgery (Thyroidectomy) FOLLOW UP Monitor serum TSH, T3 & free T4 4-6 weeks after initiation of thionamides (and after radioactive iodine therapy); then at 3-6 month intervals.  Thyroid Storm-decompensated, severe form of hyperthyroidism Decompensated, severe form of hyperthyroidism, associated with increased morbidity and mortality elevated serum thyroid hormone concentrations, resulting in the extreme alteration of usual hyperthyroid symptoms. The diagnosis can happen in patients with or without preexisting hyperthyroidism. It is a rare diagnosis and typically triggered by precipitants such as trauma, myocardial infarction, surgery (including thyroid surgery for hyperthyroidism or other surgeries in general), or infection. In some cases, acute exposure to excess iodine (administration of iodinated contrast radiographic scan) may result in iodine-induced hyperthyroidism to trigger thyroid storm. Patients with known severe hyperthyroidism who are noncompliant with prescribed antithyroid medications may also form thyroid storm. Rapid recognition of thyroid storm is necessary to start management, which should be performed in an ICU setting. Clinical manifestations include fever, cardiac arrhythmias, vomiting, and impaired mental status. (Leung, 2017)  GERIATRIC CONSIDERATIONS Given the high prevalence of hypothyroidism in women > 60 yrs & the presence of subtle symptoms, TSH screening is recommended in this age group. ◦ Elderly less likely to experience thyrotoxicosis than hypothyroidism. ◦ Most common presentation of hyperthyroidism in patients > 60 yrs is atrial fibrillation. ◦ Other atypical presentations of hyperthyroidism, including s/s of anorexia, weight loss, or weakness. In older patients, “start low & go slow” when initiating thyroid replacement therapy for hypothyroidism. Risk for treatment-induced angina, CHF, or arrhythmias (particularly atrial fibrillation) Initiate levothyroxine dose at 25 mcg PO daily & increase gradually to 1.0 mcg/kg/daily Post-menopausal women with untreated Graves disease or on thyroid replacement therapy: Prone to accelerated bone loss & osteoporosis… Important to check bone density! May require increased dosage of levothyroxine if estrogen therapy is initiated concurrently Lab interpretation review Condition TSH Free T4 T3 Other thyroid labs Normal normal normal Normal negative Primary High Low Hypothyroid Subclinical High Normal Hypothyroid Hashimotos High Low + anti-TPO antibody Primary Low High High Elevated TSI Hyperthyroid Graves Subclinical Low Normal Normal Hyperthyroid