- A clinical condition termed as anti-PIT-1 antibody syndrome, that causes autoimmunity to a pituitary-specific transcription factor, PIT-1 had been previously identified.
- This condition is associated with the presence of anti-PIT-1 antibodies and causes deficiency of acquired growth hormone (GH.), prolactin (PRL), and thyroid-stimulating hormone (TSH).
- New findings have detected the presence of thymoma, tumors originating from the thymic gland, in every case of anti-PIT-1 antibody syndrome.
The newly-identified autoimmune endocrine disease that leads to hypopituitarism is caused by thymomas, reveals study.
The findings are by a Japanese research group.
Thymomas are a type of tumor originating from the thymic gland. They are known to trigger number of autoimmune conditions like myasthenia gravis. Thymomas play a crucial role in triggering the new condition.
The research group was led by Associate Professor TAKAHASHI Yutaka, Research Fellow BANDO Hironori, and Associate Professor IGUCHI Genzo in Kobe University Graduate School of Medicine.
The immune system if the body is responsible for protecting the body against invading pathogens.
In autoimmune diseases the immune system starts to attack its own healthy cells and tissue within the body.
There are more than 80 types of autoimmune disease, including rheumatoid arthritis (which affects roughly 1% of the population), systemic lupus erythematosus, and myasthenia gravis.
Main symptoms include fatigue, muscle ache and low grade fever accompanied by inflammation.
The pituitary gland is an important gland that plays the crucial role of regulating various hormones. It is located at the base of the brain.
Anti-PIT-1 Antibody Syndrome
In previous studies, Professor Takahashi's research team discovered an autoimmune disease. This new clinical entity causes autoimmunity to a pituitary-specific transcription factor, PIT-1 that plays an essential role in producing growth hormone (GH), thyroid stimulation hormone (TSH), and prolactin (PRL).
In patients with this condition, anti-PIT-1 antibodies were detected and hence this disease was named anti-PIT-1 antibody syndrome.
Anti-PIT-1 antibody syndrome is characterized by acquired growth hormone (GH), prolactin (PRL), and thyroid-stimulating hormone (TSH) deficiencies.
The cause that led to the breakdown of immune tolerance against PIT-1 remained unclear.
Role of Thymus Gland
The new study has identified that thymoma triggers this syndrome.
Thymoma was detected in every case of anti-PIT-1 antibody syndrome. PIT-1 was abnormally expressed within the thymoma and this evoked the immune tolerance breakdown.
Cytotoxic T cells (CTLs) are a type of "killer" white blood cell that destroy tumor cells as a part of immune responses. These cells are "trained" in the thymic gland, and during these processes both positive and negative selections take place.
In the thymic cortex, T cells are trained to be able to recognize various antigens (positive selection) and in the medulla, T cells that react with self-antigens are deleted (negative selection). These sophisticated systems enable T cells to correctly target foreign antigens.
In anti-PIT-1 antibody syndrome, PIT-1 is abnormally expressed in thymoma cells, therefore T cells that react to PIT-1 are produced and an autoimmunity is triggered.
"Around 20% of hypopituitarism cases are caused by unknown factors. This discovery has clarified one of the causes," said Associate Professor Takahashi. "We hope that this discovery will contribute to more effective diagnosis and treatment for patients suffering from autoimmune pituitary diseases, hypopituitarism, and thymomas."
These findings are published in the online edition of Scientific Reports.
- Autoimmune Diseases - (https://medlineplus.gov/autoimmunediseases.html)
- TAKAHASHI Yutaka et al. A novel thymoma-associated autoimmune disease: Anti-PIT-1 antibody syndrome. Scientific Reports; (2017) doi:10.1038/srep43060