A method of improving the endogenous production of prostaglandins by a mammal is disclosed which comprises administering to the mammal an effective amount of certain 1-pyridylalkyl-3-phenylthioureas. Disclosed also are novel substituted 1-pyridylalkyl-3-phenylthioureas and therapeutic compositions thereof which are useful in carrying out the method of the invention. Disclosed also are methods of treating mammals for clinical conditions responsive to prostaglandins, such as for example, male infertility, epidermal injuries, atonic uterine bleeding, thromboembolic disease and like clinical conditions.