Researchers at Tel Aviv University discovered that a certain type of genetic deafness is caused by a deficiency in the hormone produced by the thyroid gland
The thyroid gland has a variety of vital roles in our body. It regulates the heart rate and is responsible for the metabolism, and when its function is impaired we may suffer from various and unusual symptoms: fatigue, weight gain, chills, hair loss, anxiety, increased sweating and more. Now a new study at Tel Aviv University reveals that thyroid dysfunction may also cause hereditary deafness.
The researchers, Prof. Keren Avraham and Dr. Amiel Dror from the Department of Human Molecular Genetics and Biochemistry at the Tel Aviv University School of Medicine, used advanced imaging tools and discovered that genetic deafness may be caused by a deficiency in the hormone produced by the thyroid gland during fetal development.
The study was recently published in the journal Mammalian Genome and was even chosen to appear on the cover of the journal.
What is between the thyroid gland and hearing?
"Our laboratory usually focuses on the study of the inner ear system, and dealing with the thyroid gland is a new challenge for us," says Dr. Dror. "We wanted to find out how these two systems influence each other to create normal hearing, and that's how the current study was born."
Using an electron microscope at the Sackler Center for Cellular and Molecular Imaging, the researchers followed hair cells in the cochlea - the organ of hearing in the inner ear. These are unique hair cells that sense the sound waves we hear, and translate the sound into nerve stimulation that reaches the brain. The researchers tested whether there was a difference between these hypotheses in two groups of laboratory mice: a group of mice with a genetic mutation for deafness, and a control group of healthy mice. In the mice with the mutation, disorganization of the hair cells in the ear was observed, compared to perfect organization in the control group.
The study of the inner ear in this way revealed a spectrum of structural and molecular defects that characterize hypoactivity or poor hormonal activity of the thyroid gland. Another test revealed a problem in the development of the thyroid glands of those mice: follicles marked in the thyroid gland did not grow, or grew only partially.
"Our research showed that hearing does not develop properly when the thyroid hormone is not sufficiently available, as a result of a genetic mutation," says Dr. Dror. "In the next step, we intend to supplement the missing hormone in mice suffering from the genetic defect, and check whether the treatment actually prevents hearing loss. Our model is a platform for developing new therapeutic approaches for this type of congenital deafness. The road to applied treatments is still long, but we believe we are on the right path."
Music and genetics
Dr. Dror says that he became interested in sounds and music at a young age. "I play a stringed instrument, and the quality of the sound is very important to me. As a research student in Prof. Avraham's lab, I was exposed to the wonderful world of genetics, and found an opportunity to connect the two research fields that fascinate me: genetics and hearing. As a medical student, I continued the research work, and the direct contact with patients suffering from hearing impairment motivated me to focus on the clinical significance of the research work."
As a doctor, Dr. Dror believes in the importance of engaging in research that will help his patients. "Advanced medicine is based on the combination of basic science and clinical research," he says. I hope that our research will make even a modest contribution to the global effort to improve the treatment of hearing impairments."
