Question

Your friend Bud has the talent to be a star basketball center-if only he weren't 5 foot 8 . Being wellintentioned but ignorant, you start injecting him with growth hormone as he sleeps each night. You think this is a clever strategy, but after a time you notice that he hasn't grown an inch. Instead, his jaw and forehead seem to have gotten disproportionately large and his hands and feet are swollen. Explain why the growth hormone didn't make Bud grow taller and why it had the effect it did. What disease state do these changes mimic?

Short answer

Injecting growth hormone did not make Bud grow taller because his growth plates were likely already closed after puberty, making the injections ineffective for increasing height. Instead, the injections caused other effects such as an enlarged jaw and forehead and swollen hands and feet, due to the growth hormone's impact on cartilage and connective tissue. These changes mimic the disease state of acromegaly, a hormonal disorder caused by excessive growth hormone production.

Step-by-step solution

Understand the role of growth hormone in the body

Growth hormone (GH) is a hormone produced by the pituitary gland. It is involved in the regulation of several bodily processes, mainly growth and development. Growth hormone stimulates the growth of bones and tissues, contributing to the overall height of an individual. However, the response of the body to growth hormone depends on various factors, including age and hormonal balance.

Explain why injecting growth hormone didn't make Bud grow taller

Growth hormone mainly affects the growth plates at the ends of long bones, causing them to grow longitudinally. The growth plates close after puberty, and the bones can no longer grow in length. As Bud is already in high school, it is likely that his growth plates have already closed, rendering the injections ineffective in increasing his height. The growth hormone injections wouldn't be able to reopen the growth plates or make them grow longitudinally once they are closed.

Describe the effects observed in Bud after the injections

Though growth hormone didn't increase Bud's height, it did have effects on other parts of his body. Injecting growth hormone caused an increase in the size of his jaw and forehead, as well as swelling in his hands and feet. These effects are due to the growth hormone's impact on other tissues, such as cartilage and connective tissue, which continue to respond to hormones even after the growth plates have closed.

Identify the disease state these changes mimic

The changes observed in Bud after injecting growth hormone mimic a condition called acromegaly. Acromegaly is a hormonal disorder usually caused by a pituitary tumor producing excessive GH. It leads to abnormal growth in various body parts, including the hands, feet, jaw, and forehead. The symptoms observed in Bud resemble those of an individual with acromegaly. To summarize, injecting growth hormone did not make Bud grow taller because his growth plates were likely already closed, rendering the injections ineffective for increasing his height. However, the injections did cause changes in other body parts, resembling the disease state of acromegaly.

Key concepts

Growth Plates

Growth plates, also known as epiphyseal plates, are regions of cartilage located at the ends of long bones. These plates play a crucial role during childhood and adolescence as they determine how tall a person will grow. During periods of growth, these plates add length to bones by continuously creating new cartilage, which is later replaced by bone tissue.

However, as puberty ends, the growth plates gradually close and are replaced entirely by bone. At this stage, known as epiphyseal closure, additional bone growth in terms of length is no longer possible. This is why Bud, who is likely past puberty, did not grow taller despite the injections of growth hormone. Once the growth plates have closed, no hormonal or medical intervention can stimulate further height increase.

This also helps us understand how growth hormones work—they stimulate these growth plates to increase bone length. But once those plates are no longer there, the hormone doesn't contribute to vertical growth.

Acromegaly

Acromegaly is a condition that results from prolonged excessive production of growth hormone, usually due to a pituitary tumor. This leads to an overgrowth of bones and tissues, although not an increase in height. Since Bud's height did not increase, yet his jaw and forehead seemed to grow, as well as his hands and feet becoming swollen, these symptoms closely mimic acromegaly.

In people with acromegaly, because the growth plates have already closed, growth hormone instead causes bones to thicken and soft tissues to enlarge. Typical features include larger hands and feet, changes in facial structure such as protruding jaws and enlarged nasal passages, and sometimes internal organ growth.

It's important to diagnose and treat acromegaly early to avoid complications. This condition highlights how growth hormone affects different body parts and underlines how complex hormone regulation can be.

Pituitary Gland

The pituitary gland is often referred to as the "master gland" of the endocrine system. It is a small, pea-sized structure located at the base of the brain. Despite its diminutive size, it produces several important hormones, including growth hormone, which regulates growth and metabolism.

In the context of growth hormone secretion, the pituitary gland plays a central role. It releases growth hormone in pulses, particularly during sleep, to fuel growth and development during childhood. This affects not just bone growth but also muscle and tissue growth.

If the pituitary gland overproduces growth hormone in adulthood, it can lead to conditions like acromegaly. This is different from gigantism, which occurs if the hormone is released in excess before the closure of growth plates. Thus, the careful balance and regulation exerted by the pituitary gland are vital for normal physical development and health.