A man excretes a large volume of dilute urine, leading to dehydration. He also feels very thirsty. This is primarily caused due to 

A man excretes a large volume of dilute urine, leading to dehydration. He also feels very thirsty. This is primarily caused due to  hyposecretion of ADH. ADH, produced by the hypothalamus and released by the posterior pituitary gland, helps regulate the body's water balance by promoting water reabsorption in the kidneys. When ADH levels are low (hyposecretion), the kidneys excrete more water, leading to increased urine production and dilution, along with dehydration and thirst.