A recriprocal relationship exists between the nervous system, hormones and behavior. This relationship begins early in life, when the release of hormones organizes the brain in terms of its endocrine function and in terms of establishing the appropriate connections for the control of behavior. Thyroid hormones are essential for normal development of the brain. These hormones exert a significant and crucial effect on differentiation of cells. Dr. Iwamoto found that treatment with a drug that induces lower levels of thyriod hormone during a specific period of postnatal development dramatically affects adult testis weight and sperm production. These data are quite striking. While it is known that hyper- and hypothyroidism interferes with the physiology of reproduction in females, little is known about the consequences in males. Dr. Iwamato will determine whether this gonadal hypertrophy induced by developmental hypothyroidism results from or causes a major change in hypothalamic function and sensitivity to gonadal steroids. He will compare the gonadotropin and testosterone secretory patterns, and single unit activity of hypothalamic cells in response to testosterone and estrogen, of these animals to normal males. This unique transient hypothyroidism that induces hypogonadal males may prove to be an important model for understanding the hypothalamic- pituitary-gonadal system and thus, provide new insights into the understanding and treatment of male infertility.
