Male cats produce a significant amount of the hormone testosterone, which is the primary androgen, or male sex hormone, in the feline body. Its presence is fundamental to developing the male cat’s physical attributes and expressing distinct behaviors associated with reproduction and territoriality. The concentration of this hormone largely dictates the differences seen between intact and neutered male cats.
The Feline Endocrine System and Hormone Production
The majority of testosterone in a male cat is manufactured in the testes by specialized Leydig cells. Production is regulated by the brain’s pituitary gland, which releases Luteinizing Hormone (LH) to stimulate these cells. While the testes are the main source, a small amount of testosterone is also produced by the adrenal glands.
Testosterone levels are low in young kittens but rise noticeably as the cat approaches sexual maturity. Puberty, and the corresponding spike in hormone output, typically occurs between five and ten months of age. After puberty, circulating levels in an intact adult male cat can range from 1,000 to 6,000 picograms per milliliter, often peaking seasonally during the spring breeding season.
Physical and Behavioral Effects of Testosterone
Testosterone develops the physical characteristics that distinguish an intact male cat. These secondary sex characteristics include a thicker neck and pronounced, jowly cheeks, often called “stud jowls.” The hormone also promotes increased muscle mass and the development of tiny, keratinized bumps on the penis called penile spines.
Behaviorally, the hormone drives the intense instincts associated with breeding and survival. Intact male cats frequently exhibit increased aggression, particularly toward other males, as they compete for territory and mating opportunities. This intermale aggression is a direct result of high testosterone levels and can manifest as fighting and vocalization.
The impulse to establish and defend territory is also strongly influenced by this hormone. Unneutered males are prone to urine spraying, a form of scent marking that communicates their presence to potential rivals and mates. They also develop a strong mating drive, which often leads to significant roaming and wandering behavior as they search for females in heat.
What Happens When Testosterone is Removed
The standard procedure for removing the primary source of testosterone is neutering, which involves surgically removing the testes. Following this procedure, the immediate change is a significant and rapid drop in circulating testosterone levels. Plasma concentration decreases significantly within the first week after the operation.
While hormone levels drop quickly, it takes longer for the physical and behavioral effects to diminish entirely. Testosterone levels typically continue to taper over several weeks to a couple of months. The testosterone-dependent penile spines begin to regress within two weeks and are usually gone within six to eight weeks post-neutering.
Behavioral changes are often seen over the course of a few weeks or months as the hormone tapers. Roaming, mating calls, and intermale aggression are the behaviors most likely to cease or drastically reduce. However, ingrained habits, such as urine spraying or marking, may sometimes persist, though the odor is typically less intense. Since the adrenal glands continue to produce trace amounts of androgens, the post-neutering testosterone level falls to a very low range, typically below 50 picograms per milliliter.