Hypothyroidism: from diagnosis to therapy success. A review

Abstract

Hypothyroidism is one of the most common thyroid gland disorders. The article addresses the epidemiology and classification of hypothyroidism. Hypothyroidism can have different etiologies. Deficiency of thyroid hormones leads to dysfunction of many organs and systems, manifested by numerous symptoms that can be nonspecific and mimic other diseases. Undiagnosed hypothyroidism is a risk factor for the progression of pre-existing cardiovascular diseases. The prevalence of hypothyroidism is related to the sex and age of patients. The article discusses the main causes of primary and secondary hypothyroidism. The most common cause of primary hypothyroidism is autoimmune thyroiditis, which can develop both independently or associated with other autoimmune conditions as part of the polyglandular syndrome. The causes of hypothyroidism include thyroid surgery and ablation. Transient hypothyroidism may develop in patients with destructive thyroiditis (postpartum, etc.). Thyroid insufficiency as an adverse reaction related to some drugs is discussed. The article describes the clinical symptoms of hypothyroidism. The severity of thyroid hormone deficiency determines the severity of clinical manifestations. Primary hypothyroidism is classified by severity into subclinical and manifest hypothyroidism. There are no significant clinical differences between severe primary and secondary hypothyroidism. Secondary hypothyroidism may be associated with other manifestations of hypothalamic-pituitary disorders. The challenges of diagnosing hypothyroidism, which can simulate another disease, are discussed. The final diagnosis is confirmed by several laboratory and instrumental tests. Subclinical hypothyroidism is characterized by an increase in thyroid-stimulating hormone (TSH) concentration with a normal level of free thyroxine (fT4). Manifest hypothyroidism presents with an increase in the TSH and a decrease in fT4. In secondary hypothyroidism, TSH and fT4 levels decrease. Levothyroxine sodium (L-T4) replacement therapy is used to treat hypothyroidism of any etiology.

Keywords

• hypothyroidism
• autoimmune thyroiditis
• thyroid-stimulating hormone
• thyroid hormones
• drug-induced hypothyroidism
• replacement therapy
• levothyroxine sodium