Role of hormones in forming copulatory pads

The formation of copulatory pads is entirely controlled by the interplay of sex hormones, primarily androgens.

1. Androgens (The "On" Switch):Testosterone and its more potent derivative, dihydrotestosterone (DHT), are the principal hormones that stimulate pad development. When a male frog enters the breeding season, its testes produce a surge of these androgens. They travel to the thumb pads and signal the skin cells to thicken, keratinize, and form the characteristic spines.
2. Estrogens (The "Off" Switch): Estrogens, the primary female hormones, inhibit the development of these male traits. This hormonal opposition is why female frogs do not develop nuptial pads.
3. Pituitary Hormones: The entire process is regulated by hormones from the pituitary gland, such as Luteinizing Hormone (LH), which signals the testes to produce androgens in the first place.

The seasonal growth and regression of the pads are directly tied to the cyclical rise and fall of these hormone levels.