TSHB

Congenital hypothyroidism

Researchers have identified at least 10 TSHB gene mutations involved in congenital hypothyroidism, a condition characterized by abnormally low levels of thyroid hormones starting from birth. TSHB gene mutations are the primary cause of a form of the condition called central congenital hypothyroidism, which occurs when stimulation of thyroid hormone production by the pituitary gland is impaired.

TSHB gene mutations involved in congenital hypothyroidism alter the size or shape of the thyroid stimulating hormone beta subunit. Many of the mutations affect the beta subunit's seatbelt region. Some mutations severely shorten the beta subunit, eliminating the seatbelt region partially or entirely. Other mutations change the protein building blocks (amino acids) used to make the beta subunit. As a result, the seatbelt region cannot buckle around the alpha subunit. TSHB gene mutations prevent the production of functional thyroid stimulating hormone or its release (secretion) from the pituitary gland. As a result, thyroid hormone production is not stimulated, leading to low hormone levels that are characteristic of congenital hypothyroidism. Additionally, the thyroid gland is reduced in size (hypoplastic) because its growth is not stimulated.