On this page
TSHB
thyroid stimulating hormone subunit beta
TSHB is located on the short (p) arm of chromosome 1, at band 1p13.2. Arm ratio per GRCh38 - banding schematic.
Explore chromosome 1 in the library →Available at Jeen Health
Clinical tests that include this
Overview
The TSHB gene, located on chromosome 1, encodes the beta subunit of thyroid-stimulating hormone (TSH), a key regulator of thyroid function. The pituitary gland produces TSH by combining the beta subunit encoded by TSHB with an alpha subunit shared by several other hormones. Together, these subunits form the active TSH molecule that signals the thyroid gland to produce thyroid hormones.
Thyroid hormones regulate fundamental processes including metabolism, brain development, and growth. The pituitary gland continuously monitors circulating thyroid hormone levels and releases TSH when these levels drop, maintaining hormonal balance. Pathogenic variants in TSHB disrupt this regulatory system, leading to inadequate thyroid stimulation and reduced thyroid hormone production. Such variants are recognised as a cause of central congenital hypothyroidism, a condition present from birth that can affect physical and cognitive development if untreated.
What the gene does
The TSHB protein forms the beta subunit of thyroid-stimulating hormone, a glycoprotein hormone secreted by specialised cells in the anterior pituitary gland. This beta subunit must combine with a common alpha subunit to create biologically active TSH. The beta subunit contains a distinctive structural element sometimes described as a 'buckle' or 'seatbelt' region, which wraps around the alpha subunit to stabilise the assembled hormone and enable receptor binding.
Once assembled and released into the bloodstream, TSH travels to the thyroid gland in the neck, where it binds to TSH receptors on thyroid follicular cells. This binding triggers a cascade of intracellular signals that promote thyroid gland growth and stimulate the synthesis and release of thyroid hormones, including thyroxine and triiodothyronine. The pituitary gland adjusts TSH secretion in response to circulating thyroid hormone concentrations through a negative feedback loop, ensuring appropriate metabolic regulation across varying physiological demands.
Video: Genetics 101
Chromosome location
TSHB is located on the short arm of chromosome 1 at position 1p13.2. This chromosomal region contains several genes involved in endocrine signalling and metabolic regulation. The gene comprises multiple exons that encode the 138-amino-acid beta subunit precursor, which undergoes post-translational processing and glycosylation before combining with the alpha subunit.
Protein structure
Domain architecture has not been experimentally characterised in detail for this protein. The mature TSHB protein consists of 138 amino acids following signal peptide cleavage and incorporates glycosylation sites important for hormone stability and activity. The characteristic seatbelt loop extends from the beta subunit to encircle the alpha subunit, creating the interface necessary for receptor recognition and hormone function.
Key variants
Research has identified at least ten pathogenic variants in TSHB associated with congenital hypothyroidism. These variants typically disrupt protein folding, prevent proper assembly with the alpha subunit, or impair the structural stability of the mature hormone. Because TSHB is inherited in an autosomal recessive manner, individuals with biallelic pathogenic variants experience reduced or absent TSH signalling, leading to thyroid hormone deficiency from birth.
No pathogenic or likely-pathogenic ClinVar variants recorded yet for this gene.
Associated conditions
Pathogenic variants in TSHB are a recognised cause of central congenital hypothyroidism, a form of hypothyroidism arising from inadequate pituitary stimulation of the thyroid gland rather than a primary thyroid defect. Affected individuals typically present with low thyroid hormone levels and inappropriately low or normal TSH concentrations in newborn screening or early infancy. Without timely thyroid hormone replacement therapy, congenital hypothyroidism can result in growth delays, intellectual disability, and metabolic disturbances. Early diagnosis through newborn screening programmes allows prompt treatment, which generally supports normal development.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic TSHB variants typically follow autosomal recessive inheritance.
When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.
UK clinical status
TSHB appears on several NHS Genomic Medicine Service gene panels, reflecting its clinical relevance in diagnostic pathways. The gene is included in the Congenital Hypothyroidism panel (rated green, version R145), the Intellectual Disability panel (green, version R29), and the Developmental Disorders Genotype-to-Phenotype (DDG2P) database (green). Green classification indicates strong evidence supporting the gene-disease association, and inclusion in these panels guides clinicians in interpreting genetic test results for individuals with suspected endocrine or developmental conditions.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What is the role of TSHB in thyroid function?
TSHB encodes the beta subunit of thyroid-stimulating hormone, which combines with an alpha subunit to form active TSH. This hormone signals the thyroid gland to grow and produce thyroid hormones, which regulate metabolism, growth, and brain development.
How are TSHB variants inherited?
TSHB variants follow an autosomal recessive inheritance pattern, meaning an individual must inherit a pathogenic variant from both parents to develop congenital hypothyroidism. Carriers with one variant typically have normal thyroid function.
Can congenital hypothyroidism caused by TSHB variants be treated?
Yes, congenital hypothyroidism is treatable with thyroid hormone replacement therapy. Early diagnosis through newborn screening and prompt treatment generally support normal physical and cognitive development.