Understanding Growth Hormone Regulation and Disorders

Growth hormone (GH) plays a critical role in human development and metabolism, and its secretion is closely regulated by various physiological mechanisms. Clinically, the assessment of GH status often utilizes dynamic tests like the oral glucose tolerance test (OGTT) and the insulin tolerance test (ITT). These tests help determine how the body responds to glucose and insulin, allowing healthcare professionals to evaluate GH secretion effectively.

Disorders associated with GH excess are rare, impacting about 60 individuals per million, and are primarily caused by benign tumors known as pituitary adenomas. The two most notable conditions arising from excessive GH are acromegaly and gigantism. Gigantism occurs when there is excess GH before the closure of the epiphyseal growth plates, leading to proportionate but extreme growth. In contrast, acromegaly manifests after these growth plates have fused, resulting in disproportionate growth and various physical changes.

The symptoms of GH excess can be subtle, particularly in acromegaly, where the onset of symptoms is often gradual. This can lead to a significant delay in diagnosis, sometimes spanning over a decade. Patients may experience noticeable changes in their appearance, such as enlarged extremities and facial features, alongside other health complications including increased blood pressure and signs of cardiovascular distress.

Diagnosis of GH excess involves multiple approaches. Key methods include measuring serum IGF-I levels, monitoring GH in repeated serum samples, and evaluating GH suppression in response to the OGTT. Elevated IGF-I indicates excess GH, while irregular GH levels can point to autonomous production rather than the expected pulsatile secretion. Moreover, imaging techniques like MRI can reveal the presence of macroadenomas—tumors larger than 1 cm that may invade surrounding structures.

Both acromegaly and gigantism result not only in physical changes but also in significant health risks, particularly related to cardiovascular complications. Understanding the metabolic regulation of GH and recognizing the signs of excess secretion are crucial for timely diagnosis and management of these disorders.