![]() Kembara Xtra - Medicine - Hypothyroidism Clinical and metabolic conditions brought on by reduced levels of free thyroid hormone or by resistance to hormone action may be primary (resulting from intrinsic thyroid disease) or central (secondary or tertiary from hypothalamic-pituitary disease). Subclinical conditions include serum TSH levels that are higher than the upper reference limit with normal free thyroxine (T4) and a normal hypothalamic-pituitary-thyroid axis. Overt conditions include elevated TSH levels, usually 4 to 5 Men had an incidence of 0.6/1,000 people per year compared to women's 3.5/1,000 people per year. Prevalence In an unselected U.S. population over the age of 12 with a TSH upper limit of 4.5, the National Health and Nutrition Examination Survey III (NHANES III) found subclinical hypothyroidism at 4.3% and overt hypothyroidism at 0.3%. In the Framingham Study, 5.9% of women and 2.3% of men over the age of 60 had blood TSH levels greater than 10 mIU/L. Pathophysiology and Etiology Primary: abnormalities at the thyroid gland (>95% of cases) Most frequent cause globally: lack of ambient iodine Most frequent cause in the US: Hashimoto thyroiditis (chronic autoimmune thyroiditis) is characterized by loss of thyroid function as a result of thyroid antibody-mediated autoimmune damage. The condition often progresses in a way where thyroid function is gradually lost. Radioactive iodine therapy or a total subtotal thyroidectomy for hyperthyroidism; radiotherapy or surgery for thyroid cancer, benign nodular thyroid disease, or neck malignancies; postablative/posttherapeutic: following these treatments. Transient hypothyroidism: postpartum, silent thyroiditis, de Quervain syndrome (viral) Antiepileptic medications, tyrosine kinase inhibitors (sunitinib), interleukin-2, or interferon- Central: hypothyroidism caused by insufficient stimulation by TSH of an otherwise normal thyroid gland; can be secondary (level of the pituitary) or tertiary (level of the hypothalamus) in nature. Drugs used include propylthiouracil, methimazole, lithium, ami Other etiologies include genetic abnormalities, cancers, vascular, empty sella syndrome, inflammatory, infiltrative, iatrogenic, posttrauma, or medication related. Consumptive: Triiodothyronine (T3) and T4 excessively degraded by ectopically generated type 3 iodothyronine deiodinase (rare). Risk factors include: having Down syndrome or Turner syndromes; having a personal or family history of autoimmune diseases; being pregnant or having previously experienced postpartum thyroiditis; receiving external head or neck radiation; having a history of thyroid dysfunction, radioiodine therapy, or thyroid surgery; having an abnormal thyroid examination, having a goiter, or having TPOAb positivity. Diabetes mellitus types 1 and 2, pernicious anemia, celiac disease, primary adrenal failure (Addison disease), myasthenia gravis, rheumatoid arthritis, systemic lupus erythematosus, depression, and genetic syndromes with numerous autoimmune endocrinopathies are some of the conditions that are associated with these diseases. Introducing History Symptoms can differ and be ambiguous. Lethargy, exhaustion, intolerance to the cold, diminished hearing, constipation, dry skin, muscle cramps, arthralgias, and paresthesias, as well as a slight weight increase of 4 to 11 lb (2.0 to 4.5 kg). Depression, voice change (hoarseness), menstrual irregularities, infertility, and subfertility, sleep apnea, and carpal tunnel syndrome. clinical assessment Dry, thickened skin, brittle or falling out hair, periorbital edema, nonpitting swelling of the hands and feet (myxedema), Bradycardia, delayed relaxation of deep tendon reflexes, macroglossia, and goiter (especially in those with Hashimoto thyroiditis). Age-related increases in the normal ranges of serum thyrotropin are among the geriatric considerations. Differential Diagnosis: Primary Adrenal Insufficiency; Chronic Fatigue Syndrome; Depression; Anemia; Congestive Heart Failure; Obstructive Sleep Apnea; Dementia; Initial test results from the laboratory and imaging Primary hypothyroidism is characterized by an elevated TSH (>4.5 mIU/L) and a reduction in serum free T4; central (secondary or tertiary) hypothyroidism is characterized by a decrease in TSH. Determine the free T4 or free T4 index. - Lowered serum free T4 levels - Absence of antithyroid antibodies - TRH stimulation testing, particularly if the patient has hypothalamo-pituitary disease and free T4 and/or TSH levels are below normal - Imaging of the pituitary and hypothalamus Serum free T3 or total T3 should not be used to diagnose hypothyroidism. Subclinical hypothyroidism - Elevated serum TSH (>4.5 mIU/L) - Normal serum free T4. Tests in the Future & Special Considerations Antithyroid antibodies, particularly thyroid peroxidase and antithyroglobulin antibodies, can help identify the underlying etiology of primary hypothyroidism, however they are not always required. Substances that could affect test results: - Medicines that lower TSH: Glucocorticoids, dopamine agonists, octreotide, and a thyroid supplement - Substances that raise TSH: Drugs that raise free T4 include phenytoin, amiodarone, dopamine antagonists (metoclopramide/domperidone), oral cholecystographic dyes (sodium ipodate), and excessive amounts of estrogen or androgen. Heparin and a lot of biotin ingestion Any severe disease, pregnancy, prolonged protein malnutrition, hepatic failure, or nephrotic syndrome are disorders that could affect test results. Test interpretation Screening - Patients with the above-mentioned risk factors - Patients with thyroid imaging abnormalities or laboratory abnormalities such as - Significant hyperlipidemia or a change in lipid pattern - Hyponatremia, frequently brought on by ineffective production of antidiuretic hormone - High serum muscle enzyme concentrations - Macrocytic anemia - Pericardial or pleural effusion - Disorders of the pituitary or hypothalamus Pregnant women who have a personal or familial history of thyroid illness, type 1 diabetes, recurrent miscarriages, morbid obesity, or infertility may consider getting a TPOAb. The U.S. Preventive Services Task Force found insufficient evidence for or against screening nonpregnant, asymptomatic children or adults (2)[A]. - Universal screening is not advised for individuals who are pregnant or intending pregnancy. Women with strong family histories of thyroid disease or autoimmune disease should be tested at age 19 according to ACOG recommendations. First Line of Medicine Levothyroxine (Synthroid, Levothroid): 1.5 to 1.8 g/kg/day (adjust for desired body weight) (2)[A]; titrate by 12.5 to 25.0 g/day every 4 to 8 weeks until TSH is within the normal range. - The dosage required may change depending on factors such age, gender, the thyroid gland's remaining secretory capability, other medications the patient is taking, and intestinal function (1)[A]. – The formulations may be absorbed differently when switching between a liquid, tablet, and capsule, so proceed with caution. - Due to slower clearance, elderly patients may need to take only two-thirds of the amount given to young adults. Ideally, take levothyroxine one hour before breakfast on an empty stomach. If taken at least two hours after the last meal, giving the medication before bedtime may produce higher T4 levels than giving it in the morning (4)[A]. - Drugs that prevent its absorption, such as ferrous sulfate, proton pump inhibitors, calcium carbonate, and bile acid resins, should be taken 4 hours after the T4 dose. Contraindications include overt thyrotoxicosis, untreated adrenocorticoid insufficiency, acute MI, and preexisting TSH suppression. Precautions: Start with lesser doses, such as 12.5 to 25.0 g, if you are elderly or have a history of coronary artery disease. - With the administration of T4, diabetic patients may need to alter their hypoglycemic medications. - Vitamin K antagonist dosage may need to be adjusted; when starting treatment, evaluate prothrombin time. - Patients taking digoxin may require strict observation. - Elderly adults with high thyroid hormone are more prone to AFib and osteoporotic fracture - Patients who need higher doses than predicted should be checked for GI conditions such Helicobacter pylori or celiac disease that might impair the absorption of thyroid hormones. There may be interactions between the following medicines: Iron sulfate, calcium carbonate, antacids, colestipol, sucralfate, PPI, OCPs, ciprofloxacin, and cholestyramine may reduce absorption. - Vitamin K antagonists, insulin, oral hypoglycemic medications, estrogen. If subclinical hypothyroidism should be treated, there is debate. No increase in survival, cardiovascular morbidity, or health-related quality of life was discovered by the Cochrane Review. people with iron deficiency anemia and people with TSH levels more than 10 should receive treatment for subclinical hypothyroidism. If the procedure is elective, reach euthyroid status before it. If urgent surgery is required, continue with tailored replacement therapy both before and after the procedure. There are both branded and generic T4 versions. When switching manufacturers, preparation efficacy is probably equal; if there are any concerns, serum TSH can be measured six weeks following the change in manufacturers. pregnant women's issues Replacement therapy may need to be modified; the typical dose rises from 25% to 50%. TSH levels should be checked every month throughout the first half of pregnancy and at least once during the second half; the ideal range is 2.0 to 2.5 mIU/L for the first trimester and 3.0 mIU/L for the second and third trimesters. In the postpartum period, painless subacute thyroiditis may develop, resulting in temporary hypothyroidism lasting 2 weeks to 6 months. Replacement therapy may be necessary for treatment. Up to 30% of these people experience lifelong hypothyroidism. Second Line Adding T3 to T4 has no advantages. Liothyronine (T3) or desiccated thyroid hormone (T3 and T4) may be an alternative for those who cannot take T4 alone. Desiccated thyroid hormone is not advised for the treatment of hypothyroidism. Referral Infants and young children Women who are pregnant or trying to get pregnant Goiter, nodule, or other structural alterations in the thyroid gland Adrenal or pituitary diseases Myxedema coma (decompensated severe untreated hypothyroidism), arrhythmias that could be deadly, pericardial or pleural effusion, and hypotension are all reasons for admission. Patient Follow-Up Monitoring TSH and free T4 levels should be checked every 4 to 8 weeks after starting treatment or following a dose modification. Once the condition has stabilized, periodic TSH levels should be checked after six months, then every 12 months, or more frequently if clinically necessary. Observe the condition of the heart in older patients. Check TSH more frequently if you start taking estrogen supplements, are pregnant, or have experienced significant weight changes. TSH is unreliable in central hypothyroidism; free T4 must be monitored instead. In people with euthyroidism, thyroid hormones shouldn't be utilized to treat obesity. Patient Education – Outline the necessity of ongoing thyroid replacement therapy. For individuals taking various drugs that can interact, more information is necessary. Tell patients to notify their doctors of any infection-related symptoms or heart-related problems. List symptoms of thyrotoxicity. Prognosis: It's usually possible to get back to normal. If treatment is stopped, relapses will happen. Severe cases may develop into myxedema coma if left untreated. Complications The mortality and complication rates following surgery are comparable for people with mild to moderate hypothyroidism and euthyroid patients. 30–60% mortality rate from myxedema coma Megacolon, sexual dysfunction, infertility, organic psychosis, a sad mood, and apathy are just a few of the symptoms. Opiate hypersensitivity Long-term treatment may cause a reduction in bone mineral density. Iatrogenic thyrotoxicosis can cause osteoporosis and AFib. When levothyroxine is started before steroids in patients with untreated adrenal insufficiency, it can cause an adrenal crisis. It can also cause treatment-induced congestive heart failure in people with coronary artery disease (small risk).
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