SLC26A4-related sensorineural hearing loss (SLC26A4-SNHL), characterized by inner ear malformations also associated with vestibular dysfunction, comprises two phenotypes: (1) nonsyndromic SLC26A4-SNHL (also referred to as DFNB4 or nonsyndromic enlargement of the vestibular aqueduct [NSEVA]) and (2) Pendred syndrome (PDS) that includes thyroid involvement (typically identified more frequently in countries without universal salt iodization programs). The time of onset and type of presentation of the SNHL vary (such that some newborns pass their newborn hearing screening); however, by age three years most children have bilateral and severe-to-profound hearing loss. Manifestations of vestibular dysfunction (such as head-tilting, vomiting, and/or delayed ambulation or clumsiness in a child who previously walked well) can precede or accompany the fluctuations in hearing typical of this disorder. Thyroid enlargement (goiter) occurs gradually and is typically evident in the second decade, especially if iodine is not routinely included in the diet.

A rare hyperthyroidism characterized by mild to severe hyperthyroidism, presence of goiter, absence of features of autoimmunity, frequent relapses while on treatment and a positive family history.

Neonatal diabetes mellitus with congenital hypothyroidism (NDH) syndrome is characterized by intrauterine growth retardation and onset of nonimmune diabetes mellitus within the first few weeks of life. Other features include renal parenchymal disease, primarily renal cystic dysplasia, and hepatic disease, with hepatitis in some patients and hepatic fibrosis and cirrhosis in others. Facial dysmorphism, when present, consistently involves low-set ears, epicanthal folds, flat nasal bridge, long philtrum, and thin upper lip. Most patients exhibit developmental delay (Dimitri et al., 2015).

Congenital hypothyroidism occurs when the thyroid gland fails to develop or function properly. In 80 to 85 percent of cases, the thyroid gland is absent, severely reduced in size (hypoplastic), or abnormally located. These cases are classified as thyroid dysgenesis. In the remainder of cases, a normal-sized or enlarged thyroid gland (goiter) is present, but production of thyroid hormones is decreased or absent. Most of these cases occur when one of several steps in the hormone synthesis process is impaired; these cases are classified as thyroid dyshormonogenesis. Less commonly, reduction or absence of thyroid hormone production is caused by impaired stimulation of the production process (which is normally done by a structure at the base of the brain called the pituitary gland), even though the process itself is unimpaired. These cases are classified as central (or pituitary) hypothyroidism.\n\nCongenital hypothyroidism can also occur as part of syndromes that affect other organs and tissues in the body. These forms of the condition are described as syndromic. Some common forms of syndromic hypothyroidism include Pendred syndrome, Bamforth-Lazarus syndrome, and brain-lung-thyroid syndrome.\n\nSigns and symptoms of congenital hypothyroidism result from the shortage of thyroid hormones. Affected babies may show no features of the condition, although some babies with congenital hypothyroidism are less active and sleep more than normal. They may have difficulty feeding and experience constipation. If untreated, congenital hypothyroidism can lead to intellectual disability and slow growth. In the United States and many other countries, all hospitals test newborns for congenital hypothyroidism. If treatment begins in the first two weeks after birth, infants usually develop normally.\n\nCongenital hypothyroidism is a partial or complete loss of function of the thyroid gland (hypothyroidism) that affects infants from birth (congenital). The thyroid gland is a butterfly-shaped tissue in the lower neck. It makes iodine-containing hormones that play an important role in regulating growth, brain development, and the rate of chemical reactions in the body (metabolism). People with congenital hypothyroidism have lower-than-normal levels of these important hormones.

Generalized thyroid hormone resistance (GRTH) is characterized by elevated serum levels of free thyroid hormones with inappropriately elevated thyroid-stimulating hormone (TSH) as well as clinical and biochemical evidence of decreased thyroid hormone action. Affected individuals also show unresponsiveness to large doses of exogenous thyroid hormones (summary by Parrilla et al., 1991).