Hypothyroidism: A Review

Importance: Hypothyroidism is a disease of thyroid hormone deficiency. The prevalence ranges from 0.3% to 12% worldwide, depending on iodine intake, and it is more common in women and older adults. Untreated hypothyroidism can cause serious health complications such as heart failure and myxedema coma.

Observations: Hashimoto thyroiditis (an autoimmune disease) is the cause of primary hypothyroidism in up to 85% of patients with hypothyroidism living in areas with adequate nutritional iodine levels. The risk of developing hypothyroidism is associated with genetic factors (having a first-degree relative with hypothyroidism), environmental factors (iodine deficiency), undergoing neck surgery or receiving radiation therapy, pregnancy in the setting of underlying autoimmune thyroid disease, and with the use of certain medications (eg, immune checkpoint inhibitors and amiodarone). Patients with hypothyroidism may have nonspecific symptoms due to metabolic slowing, including fatigue (68%-83%), weight gain (24%-59%), cognitive issues (45%-48%) such as memory loss and difficulty concentrating, and menstrual irregularities (approximately 23%) such as oligomenorrhea and menorrhagia. Hypothyroidism can cause insulin resistance and hyperglycemia in patients with diabetes, increase the risk for cardiovascular events, such as heart failure, and negatively affect female reproductive health, causing disrupted ovulation, infertility, and increased risk of miscarriage. Untreated hypothyroidism may progress to severe hypothyroidism with decompensation (myxedema coma), which is a condition associated with hypothermia, hypotension, and altered mental status that requires treatment in an intensive care unit and has a mortality rate of up to 30%. Hypothyroidism is diagnosed based on biochemical testing; a high thyrotropin (TSH) level and a low free thyroxine (T4) level indicate overt primary hypothyroidism. Screening for hypothyroidism is not recommended for asymptomatic individuals. Targeted testing is recommended for patients who are considered high risk (eg, patients with type 1 diabetes). First-line treatment for hypothyroidism is synthetic levothyroxine to normalize thyrotropin levels. Initial dosages should be tailored to patient-specific factors. Lower starting doses should be used for older patients or those with atrial fibrillation and coronary artery disease. Thyrotropin monitoring should be performed 6 to 8 weeks after initiating levothyroxine treatment, or when changing the dose, and then annually once the thyrotropin level is at goal to avoid overtreatment or undertreatment, both of which are associated with cardiovascular health risks.

Conclusions and relevance: Hypothyroidism may be associated with fatigue, weight gain, memory loss, difficulty concentrating, cardiovascular disease such as heart failure, menstrual irregularities, infertility, and increased risk of miscarriage. Levothyroxine is the first-line treatment to normalize the thyrotropin level and improve clinical manifestations due to hypothyroidism.

Author/s:

Layal Chaker, Maria Papaleontiou

Thyroid Cancer: A Review

Erin Blanchette — Mon, 19 Feb 2024 16:44:44 +0000

Date Added:

February 19, 2024

Journal/Publication:

JAMA

Publisher:

American Medical Association

Publication Date:

February 6, 2024

Issue:

Volume:

331

Pages:

425-435

URL:

Thyroid Cancer: A Review

Type:

Meta-analyses, Reviews, and Guidelines

Format:

Article

DOI (1):

10.1001/jama.2023.26348

Keywords

Targeted and Immune Therapy

PMID (1):

38319329

MeSH

Thyroid Epithelial Cells

An update on thyroid cancer detection, types, and treatment. James W. Mold, MD, MPH

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Importance: Approximately 43 720 new cases of thyroid carcinoma are expected to be diagnosed in 2023 in the US. Five-year relative survival is approximately 98.5%. This review summarizes current evidence regarding pathophysiology, diagnosis, and management of early-stage and advanced thyroid cancer.

Observations: Papillary thyroid cancer accounts for approximately 84% of all thyroid cancers. Papillary, follicular (≈4%), and oncocytic (≈2%) forms arise from thyroid follicular cells and are termed well-differentiated thyroid cancer. Aggressive forms of follicular cell-derived thyroid cancer are poorly differentiated thyroid cancer (≈5%) and anaplastic thyroid cancer (≈1%). Medullary thyroid cancer (≈4%) arises from parafollicular C cells. Most cases of well-differentiated thyroid cancer are asymptomatic and detected during physical examination or incidentally found on diagnostic imaging studies. For microcarcinomas (≤1 cm), observation without surgical resection can be considered. For tumors larger than 1 cm with or without lymph node metastases, surgery with or without radioactive iodine is curative in most cases. Surgical resection is the preferred approach for patients with recurrent locoregional disease. For metastatic disease, surgical resection or stereotactic body irradiation is favored over systemic therapy (eg, lenvatinib, dabrafenib). Antiangiogenic multikinase inhibitors (eg, sorafenib, lenvatinib, cabozantinib) are approved for thyroid cancer that does not respond to radioactive iodine, with response rates 12% to 65%. Targeted therapies such as dabrafenib and selpercatinib are directed to genetic mutations (BRAF, RET, NTRK, MEK) that give rise to thyroid cancer and are used in patients with advanced thyroid carcinoma.

Conclusions: Approximately 44 000 new cases of thyroid cancer are diagnosed each year in the US, with a 5-year relative survival of 98.5%. Surgery is curative in most cases of well-differentiated thyroid cancer. Radioactive iodine treatment after surgery improves overall survival in patients at high risk of recurrence. Antiangiogenic multikinase inhibitors and targeted therapies to genetic mutations that give rise to thyroid cancer are increasingly used in the treatment of metastatic disease.

Author/s:

Laura Boucai, Mark Zafereo, Maria E Cabanillas