Testosterone, the primary male sex hormone, plays an important role in the development of secondary sex characteristics in boys during puberty, including deepening of the voice and growth of the larynx or Adam’s apple. The Adam’s apple is a feature of the larynx, or voice box, that becomes prominent during male puberty due to enlargement of the thyroid cartilage under the influence of testosterone. But what exactly causes this growth and is testosterone alone responsible for the Adam’s apple?
What is the Adam’s apple?
The Adam’s apple is a protrusion in the front of the neck formed by the angle of the thyroid cartilage surrounding the larynx. It is a secondary sex characteristic seen in males during and after puberty, although it can be visible in some females as well. The larynx grows larger and the thyroid cartilage becomes more prominent under the influence of testosterone during male puberty, leading to the characteristic “Adam’s apple” shape.
The thyroid cartilage is the largest of the nine cartilages that make up the laryngeal skeleton. It consists of two laminae fused together at an angle in the front, creating the protruding V-shape. The function of the thyroid cartilage is to protect the vocal folds within the larynx and act as an attachment point for muscles involved in speech and swallowing. Enlargement of the thyroid cartilage expands the larynx and deepens the voice in males.
The role of testosterone
Testosterone is the key hormone responsible for most male secondary sex characteristics that develop during puberty. In males, testosterone is primarily secreted by the testes. It signals the growth and maturation of the testes, penis, and prostate as well as body hair growth, increased muscle mass, bone growth, and deepening of the voice.
One of the major effects of rising testosterone levels during puberty is enlargement of the larynx and associated structures, including the thyroid cartilage. Testosterone causes growth of the laryngeal cartilages and vocal folds, resulting in enlargement of the voice box. The thyroid cartilage grows faster and to a greater degree than the other cartilages, creating the protruding Adam’s apple shape in males.
Testosterone initiates the growth spurt of the larynx and maintains its enlarged size once puberty completes. The male larynx is approximately 50% larger than the female larynx on average. This growth accounts for the dramatic deepening of the male voice and development of the Adam’s apple during puberty.
Other hormones involved
Although testosterone is the major driver of laryngeal enlargement, other hormones also play a role in this process:
- Growth hormone – Works together with testosterone to bring about growth of the thyroid cartilage.
- Insulin-like growth factor 1 (IGF-1) – Mediates the growth-promoting effects of growth hormone on the laryngeal cartilages.
- Estrogens – Female sex hormones that inhibit the growth of the larynx and contribute to the smaller size in women.
The influence of testosterone and other hormones results in clear differences in larynx size between males and females by the end of puberty. On average, the adult male larynx measures around 6 cm in length compared to the female larynx which measures around 4 cm. This accounts for gender differences in vocal pitch and prominence of the Adam’s apple.
Changes during male puberty
The development of the Adam’s apple occurs in distinct stages over the course of puberty in males:
- Prior to puberty, the male and female larynx are similar in size.
- Rising testosterone levels cause initial growth of the larynx and thyroid cartilage starting around age 11-13 years.
- The thyroid cartilage grows rapidly for 2-3 years, causing the voice to drop and Adam’s apple to enlarge around age 14-16 years.
- Final enlargement and ossification (hardening) of the laryngeal cartilages occurs by late puberty around age 15-18 years, completing Adam’s apple growth.
This pattern of larynx enlargement results in the characteristic deepening of the male voice and prominence of the Adam’s apple seen after completion of puberty. The following table summarizes the changes in the male larynx during puberty:
| Age | Changes |
|---|---|
| 11-13 years | Initial testosterone-induced growth of larynx and thyroid cartilage |
| 14-16 years | Rapid thyroid cartilage enlargement, voice deepening, Adam’s apple growth |
| 15-18 years | Final enlargement and ossification of laryngeal cartilages, completion of Adam’s apple |
Genetic and environmental factors
While testosterone clearly drives enlargement of the larynx during male puberty, other factors can influence the degree of Adam’s apple growth between individuals including:
- Genetics – Larynx size is highly heritable, with up to 80% attributed to genetic factors. Certain populations show distinct enlargement.
- Body size – Taller males tend to have larger larynges and more prominent Adam’s apples.
- Smoking – Can limit larynx growth in teenagers and lead to a less prominent Adam’s apple.
- Chronic laryngitis – May cause excess growth of the laryngeal cartilages.
The prominence of the Adam’s apple ranges considerably among adult males due to differences in the underlying genetics and environmental influences on larynx growth. However, testosterone exposure during puberty remains the primary determinant leading to enlargement of the thyroid cartilage and male Adam’s apple.
Role in gender affirmation
Because the Adam’s apple is a major visible feature of the male physique, masculinization of the larynx is an important aspect of gender affirmation procedures in transgender men. Testosterone therapy typically results in significant growth of the larynx and development of an Adam’s apple within the first 6-12 months of treatment.
In some cases where testosterone alone does not induce sufficient enlargement, thyroid cartilage augmentation procedures can be performed to increase the size and protrusion of the Adam’s apple. This may help improve dysphoria and create a more masculine-appearing neck profile.
Adam’s apple reduction procedures
At the other end of the spectrum, an enlarged or prominent Adam’s apple is often a source of gender dysphoria in transgender women. A number of surgical approaches exist to reduce the size and protrusion of the thyroid cartilage to feminize the neck:
- Thyroid chondroplasty – Reshaping or shaving down the thyroid cartilage prominence.
- Tracheal shave – Reducing the cartilage volume by shaving its anterior surface.
- Laryngoplasty – Reducing the thyroid angle to make it less prominent.
These procedures, along with voice feminization surgery, are options for transgender women seeking to reduce masculine features of the larynx and upper neck region as part of gender affirmation.
Conclusion
In summary, the Adam’s apple is the result of enlargement of the thyroid cartilage surrounding the larynx in males under the influence of testosterone during puberty. While testosterone is the major driver, other hormones and local factors can modulate the degree of Adam’s apple growth. Development of this masculine laryngeal feature is an integral part of male pubertal maturation.