The Van Meter Award receives support from Mary Ann Liebert, Inc., publishers of the journal Thyroid.
Dr. Yoshimura's remarkable contributions to thyroid research relate to a series of fascinating discoveries made in birds, mammals, and fish that link photoreceptors in the brain to thyroid hormone-based regulation of seasonal reproduction. He holds a Ph.D. in Agricultural Sciences and is a Professor in the Graduate School of Bioagricultural Sciences and Director of the Avian Bioscience Research Center at University of Nagoya, Japan. Sparking Dr. Yoshimura's interest in the thyroid and thyroid hormones was his seminal discovery in birds--published in Nature in 2003--that the light-induced conversion of thyroxine (T4) to triiodothyronine (T3) in the brain regulates gonadal activity as the days get longer and shorter. He then identified the molecular mechanism associated with this phenomenon, which involves the enzyme deiodinase 2, and went on to show that extended daylight induced the synthesis of the same enzyme in mammals, suggesting that the mechanism regulating seasonal reproduction had been conserved throughout evolution.
Systems biology analytical methods led to the unexpected finding in birds that thyroid stimulating hormone (TSH) secreted from the pituitary gland is the "springtime hormone" that triggers expression of DIO2 ,the gene that controls deiodinase 2 production in the hypothalamus. Dr. Yoshimura then demonstrated that in mammals, TSH produced by the pituitary gland mediates the action of the pineal hormone melatonin, which had previously been shown to play a crucial role in regulating seasonal reproduction. More recently, Dr. Yoshimura's group has uncovered the regulatory mechanism by which TSH secreted by two different compartments of the pituitary gland can carry out different regulatory activities without functional crosstalk
Further pursuing this line of investigation, Dr. Yoshimura subsequently described the mechanism for seasonal regulation of TSH and DIO2 in fish, describing the physiological role of the saccus vasculosus as a seasonal sensor in fish.
This comprehensive body of work is likely to have a great impact on future research related to human reproductive health and mood disorders, such as seasonal affective disorder (also known as SAD or winter depression).