The aim of our study was to compare the effects of a gold salt (sodium tetrachloroaurate) and gold nanoparticles colloidal solution on the morphofunctional state of the hypothalamus and adrenal glands of 6-month-old male rats with obesity, which was induced using a diet-induced model of metabolic disorders. The rats, modeled for obesity, were divided into three groups that received a NaCl solution, gold salt solution and colloidal solution of gold nanoparticles for 10 days. Rats of the control group received a standard diet. After the end of the experiment, the hypothalamic nuclei and adrenal glands, prepared according to the appropriate histological methods, were collected from the animals. In the paraventricular nucleus of the hypothalamus, a small-cell area of neurons was examined. In the adrenal glands, cells of three zones of the cortex were examined: glomerular, fascicular, and reticular. The results of the study showed that obesity led to the increase of functional activity in the nuclei of neurons in the small-cell region of the paraventricular nucleus of the rat hypothalamus. Functional activity increased maximally in the cells of the glomerular zone of the adrenal cortex, moderately increased in the fascicular zone, and no significant changes were recorded in the reticular zone. It was shown that the gold salt caused a decrease in the functional activity of neurons of the paraventricular nucleus of the hypothalamus in obese rats. In the glomerular zone of the adrenal cortex, the functional activity of cells significantly decreased; in the fascicular zone, the parameters of cell nuclei decreased to a greater extent; in the reticular zone, there were almost no changes. The introduction of gold nanoparticles colloidal solution caused the intensification of functional activity of the paraventricular hypothalamic nucleus cells in obese rats. In the glomerular zone of the adrenal cortex, cell parameters decreased; in the fascicular zone, cytoplasmic parameters decreased, but nuclear parameters did not change; in the reticular zone, measured values of nuclei increased and cytoplasmic parameters remained unchanged. In general, the administration of gold nanoparticles colloidal solution produced more pronounced effects than gold salt solution on cells of the paraventricular nucleus of the hypothalamus and the adrenal cortex in obese rats.