Hormonal Control of Pelage Cycles in the Mink

The study on mink (Mustela vison) demonstrated that the pituitary gland was essential for normal pelage cycles. Hypophysectomized mink exhibited asynchronous and continuous molting, maintaining a winter-like coat, unlike intact controls that followed normal hair changes. Hormonal treatments, including pregnant mare serum, luteinizing hormone, follicle-stimulating hormone, and ovine gonadotrophin, did not induce summer pelage growth in either intact or hypophysectomized mink. Gonadectomy did not affect seasonal pelage changes, and thyroid-stimulating hormone failed to induce summer hair regrowth. Bilateral adrenalectomy accelerated spring pelage change, while hydrocortisone inhibited it. Corticotrophin stimulated melanogenesis in hypophysectomized mink, resulting in summer-type hair growth, contrasting with controls that regrew winter-type hair.