What Causes Acromegaly? Understanding the Origins and Symptoms of Excess Growth Hormone
Acromegaly is a rare but serious hormonal disorder that occurs when the body produces too much growth hormone (GH) after adulthood. Unlike gigantism, which happens in children before the growth plates in bones have closed, acromegaly develops in adults whose bone growth has already stopped. Because the epiphyseal plates are fused, excess GH leads to abnormal enlargement of bones and tissues in a lateral or "thickening" pattern rather than lengthwise growth.
Primary Cause: Pituitary Adenomas
The vast majority of acromegaly cases—around 98%—are caused by a benign tumor in the pituitary gland known as a pituitary adenoma. These tumors originate in the anterior pituitary and secrete excessive amounts of growth hormone. Over time, this surplus hormone triggers changes throughout the body, especially in the hands, feet, face, and internal organs. The tumor may also press on surrounding brain structures, leading to secondary complications such as vision problems or headaches.
How Pituitary Tumors Disrupt Hormonal Balance
Pituitary adenomas grow slowly, often over several years, which means symptoms of acromegaly can develop gradually and go unnoticed for a long time. As the tumor enlarges, it not only increases GH production but may interfere with the secretion of other essential hormones like thyroid-stimulating hormone (TSH), cortisol-regulating ACTH, or sex hormones. This disruption can lead to fatigue, weight gain, sexual dysfunction, and metabolic issues beyond the physical changes associated with acromegaly.
Less Common Causes: Ectopic Sources of GHRH and GH
While pituitary tumors are the dominant cause, there are rarer origins of acromegaly. In some cases, tumors located outside the pituitary—such as in the pancreas, lungs, or adrenal glands—can produce growth hormone-releasing hormone (GHRH). This GHRH travels through the bloodstream and stimulates the pituitary to overproduce growth hormone, mimicking the effects of a pituitary tumor. Even more rarely, certain non-pituitary tumors may directly secrete growth hormone, though this is highly unusual.
Diagnosing Non-Pituitary-Driven Acromegaly
When imaging shows no pituitary mass, doctors may investigate ectopic sources using CT scans, MRIs, or PET scans of the chest and abdomen. Blood tests measuring both GH and GHRH levels help differentiate between pituitary and non-pituitary causes. Identifying these rare tumors is crucial, as their treatment differs significantly from standard pituitary-directed therapies.
Recognizing the Physical and Systemic Symptoms
One of the most striking aspects of acromegaly is its distinct physical presentation. Patients often experience progressive enlargement of the hands and feet, requiring larger rings, gloves, or shoes over time. Facial changes include a protruding brow, enlarged nose, thickened lips, and an extended lower jaw (prognathism), which alters facial contours dramatically.
Beyond appearance, acromegaly affects multiple body systems. Joint pain and arthritis are common due to cartilage overgrowth. Skin becomes thicker, oilier, and may develop skin tags. Voice deepens because of vocal cord thickening. Internal organs such as the heart, liver, and kidneys may enlarge, increasing the risk of hypertension, sleep apnea, diabetes, and cardiovascular disease.
Neurological and Sensory Complications
As the pituitary tumor expands, it can compress the optic chiasm—the nerve pathway responsible for vision—leading to partial vision loss, typically in the peripheral field. Headaches are also frequent, often described as dull and persistent, originating from increased pressure within the skull.
Why Early Detection Matters
Because symptoms evolve slowly, acromegaly is often diagnosed years after onset, sometimes up to a decade later. Delayed diagnosis increases the risk of irreversible damage and comorbidities. Raising awareness among primary care providers and patients about subtle signs—like changing shoe size or facial features—can lead to earlier testing and intervention.
Testing usually involves measuring insulin-like growth factor 1 (IGF-1) levels, followed by an oral glucose tolerance test to confirm failure in GH suppression—a hallmark of acromegaly. Imaging then confirms the presence and location of any tumors.
In summary, while acromegaly is primarily driven by pituitary adenomas, understanding the full spectrum of potential causes—from ectopic hormone production to rare neoplasms—is essential for accurate diagnosis and effective treatment. Recognizing both the visible and systemic symptoms empowers timely medical evaluation and improves long-term outcomes for individuals affected by this complex condition.