More than just a polyp: Hidden acromegaly behind a giant colonic mass

Abstract

Acromegaly is a rare endocrine disorder characterized by chronic hypersecretion of growth hormone and insulin-like growth factor-1, leading to an increased incidence of colonic polyps and neoplasia. This report describes a 38-year-old man who presented with gastrointestinal symptoms and was found to have a giant sessile polyp in the colon. Routine preoperative evaluation revealed elevated serum insulin-like growth factor-1 and unsuppressed growth hormone levels, leading to the diagnosis of acromegaly, which was confirmed by a pituitary MRI that showed a macroadenoma. This case highlights that unusually large colonic polyps in younger patients should prompt consideration of systemic etiologies, including endocrine disorders. A multidisciplinary approach, integrating gastroenterological and endocrinological assessment, is essential for early diagnosis and management to reduce morbidity.

Clinical message

In young patients presenting with large colonic polyps, especially with subtle acromegaloid features, clinicians should consider screening for acromegaly. Early endocrine workup and imaging can reveal underlying pathology and guide curative management.

Introduction

Acromegaly is an endocrine disorder primarily resulting from chronic hypersecretion of growth hormone (GH), most often due to a pituitary macroadenoma. ¹ . This excessive secretion leads to elevated insulin-like growth factor-1 (IGF‑1) levels that drive a spectrum of systemic manifestations including acral overgrowth, soft tissue hyperplasia, and multisystem-associated comorbidities such as diabetes mellitus, hypertension, and sleep apnea. ²

Furthermore, acromegaly is associated with a higher prevalence of colonic lesions. While earlier studies reported that ~13% of patients present with colonic polyps, more recent data indicate a prevalence ranging from 6% to 45%, depending on population characteristics and the intensity of surveillance protocols. ³

Although the classic clinical presentation of acromegaly includes noticeable physical changes ⁴ – such as enlarged hands, feet, jaw, and coarsening of facial features – subtle manifestations may go unnoticed, resulting in diagnostic delays. ⁵

In some cases, non-endocrine complaints prompt further investigation, which can eventually unmask the underlying acromegaly. ⁶ The present case report describes a unique clinical scenario where a 38-year-old male patient, initially presenting with a giant colonic mass, was incidentally diagnosed with acromegaly. The case emphasizes the importance of maintaining a high index of suspicion for acromegaly in patients with colonic lesions and demonstrates the need for multidisciplinary collaboration to achieve timely diagnosis and appropriate management.

Case presentation

A 38-year-old male with no significant past medical history was referred to the gastroenterology clinic. His family history was noncontributory for both gastrointestinal and endocrine disorders. His HIV status was negative. On further questioning, he noted subtle changes in his facial features and enlargement of his hands over the past 2 years. Physical examination revealed subtle acral enlargement, specifically spade-like hands and thickened fingers. Other manifestations of acromegaly, such as carpal tunnel syndrome, hyperhidrosis, arthralgia, and sleep apnea symptoms, were also assessed and found to be absent.

Colonoscopy revealed a giant sessile polyp measuring ~5 cm in greatest diameter in sigmoid colon, with irregular, nodular surface features raising concern for neoplastic transformation (Figure 1). Biopsies confirmed a benign polyp with low-grade dysplasia, raising concern due to its large size.

Figure 1.

Colonoscopy revealed a giant sessile polyp (black arrow) measuring ~5 cm in greatest diameter in sigmoid colon, with irregular, nodular surface features.

During the preoperative evaluation for endoscopic resection of the colonic lesion, routine laboratory tests were performed (Table 1). The results demonstrated a markedly elevated serum IGF-1 level of 850 ng/mL (reference range for age 38: 115–307 ng/mL). In parallel, the GH suppression test using an oral glucose tolerance test (OGTT) showed a baseline GH of 15.2 ng/mL with a nadir GH of 8.7 ng/mL at 120 min. Using a conventional immunoassay, the failure to suppress GH to <0.4 ng/mL fulfilled the biochemical criteria for acromegaly diagnosis.

Table 1.

Biochemical evaluation results.

Parameter	Value	Reference range
IGF-1	850 ng/mL	115–307 ng/mL (age 38)
Baseline GH	15.2 ng/mL	<5 ng/mL
GH nadir (OGTT 120 min)	8.7 ng/mL	<0.4 ng/mL
Prolactin	18 ng/mL	4–15 ng/mL
TSH	2.1 mIU/L	0.4–4.0 mIU/L
Free T4	1.2 ng/dL	0.8–1.8 ng/dL
Morning cortisol	14.5 μg/dL	5–25 μg/dL
Fasting glucose	118 mg/dL	<100 mg/dL
HbA1c	6.8%	<5.7%

GH: growth hormone; IGF-1: insulin-like growth factor-1; OGTT: oral glucose tolerance test.

Pituitary MRI (Figure 2) revealed a 1.8 cm pituitary macroadenoma with minimal suprasellar extension and no invasion of the cavernous sinuses or optic chiasm. The tumor demonstrated typical enhancement characteristics on post-contrast imaging, confirming a surgically resectable lesion suitable for transsphenoidal approach.

Figure 2.

Pituitary MRI revealed a 1.8 cm pituitary macroadenoma (green circle) with minimal suprasellar extension and no invasion of the cavernous sinuses or optic chiasm.

Formal visual field testing was performed and revealed no visual field defects, consistent with the minimal suprasellar extension noted on imaging. Ophthalmological examination showed normal optic discs with no evidence of optic chiasm compression.

Given the dual clinical concerns, the patient was managed on two parallel fronts. The giant colonic polyp was successfully removed by endoscopic resection. The procedure was uneventful, and histopathological examination confirmed a benign adenomatous polyp with areas of low-grade dysplasia.

Following confirmation of acromegaly, the patient was referred to a multidisciplinary pituitary center. He subsequently underwent endoscopic transsphenoidal resection of the pituitary macroadenoma. The surgery was uncomplicated and curative, with the tumor fully resected and no evidence of invasion into surrounding structures.

Follow-up and outcome

At the 3-month postoperative follow-up, the patient exhibited significant clinical improvement. Serum IGF-1 decreased from 850 to 285 ng/mL (now within the age-adjusted reference range of 115–307 ng/mL), and random GH was 1.8 ng/mL. The patient reported regression of some acromegalic features, including reduced hand swelling and improved sleep quality, with improvements in glucose metabolism (HbA1c decreased from 6.8% to 5.9%). Moreover, the gastrointestinal symptoms resolved completely post-polypectomy, with no recurrence of abdominal complaints. He expressed great satisfaction with the outcome, noting a significant improvement in his overall well-being. The patient remains under vigilant long-term endocrinological and gastroenterological follow-up. His endocrinological surveillance plan includes annual monitoring of IGF-1 and GH levels, with a follow-up pituitary MRI every 2 years. As per current guidelines for patients with acromegaly, he will undergo colonoscopic surveillance every 5 years.

Discussion

Acromegaly is primarily driven by a GH-secreting pituitary adenoma, which leads to continuous stimulation of hepatic IGF‑1 production. ⁷ The resultant hypersecretion of IGF‑1 accounts for the diverse clinical manifestations seen in patients, ranging from soft tissue and skeletal overgrowth to metabolic disturbances including insulin resistance and dyslipidemia. ⁸ Typically, the onset is insidious; therefore, many patients have a prolonged duration of undiagnosed disease, which can lead to irreversible complications and an increased mortality risk. ⁹

Several endocrine societies advocate the use of serum IGF‑1 measurement as the preferred screening test for acromegaly, with the failure to suppress GH during an OGTT serving as a confirmatory diagnostic criterion. ⁴ The prognosis of acromegaly is significantly influenced by the timing of diagnosis; early detection and treatment are associated with better outcomes and reduced morbidity and mortality, whereas delayed diagnosis can lead to irreversible complications. ⁴ In the current case, the incidental discovery of elevated IGF‑1 levels during routine preoperative testing was pivotal in prompting further evaluation for acromegaly.

A growing body of evidence has suggested that patients with acromegaly are at an increased risk for developing colonic lesions, including polyps and colorectal cancer. ¹⁰ Data from the Liège Acromegaly Survey (LAS) Database, which represents one of the largest international registries, indicate that ~13% of acromegaly patients have colonic polyps at diagnosis, and a small percentage may harbor colorectal cancer. ¹¹ The pathophysiological mechanism underlying this association may relate to the mitogenic and anti-apoptotic effects of IGF‑1 on colonic epithelial cells, promoting cellular proliferation and potentially neoplastic transformation. ¹²

In our case, the presence of a giant colonic polyp served as the trigger for a broader systemic investigation. Although colonic polyps are common in the general population, the unusual size of the lesion in a relatively young patient, combined with subtle clinical signs of acromegaly, should serve as a red flag to clinicians. ¹³ Early identification of such atypical presentations is critical because delayed diagnosis of acromegaly is associated with worse outcomes and increased surgical morbidity. ¹⁴

The diagnostic approach for acromegaly involves a careful synthesis of clinical, biochemical, and radiological data. ¹⁵ In this case, the detection of high IGF‑1 levels and the lack of GH suppression on OGTT directed the workup toward a pituitary origin. The subsequent MRI provided definitive evidence of a macroadenoma, allowing for targeted therapeutic planning. The integration of gastroenterological and endocrinological evaluations was crucial in this scenario, highlighting the value of a multidisciplinary clinic in managing complex medical cases.

Recent research has explored the utility of serum biomarkers for the detection of colonic polyps in patients with acromegaly. A systematic review and meta-analysis by Ji et al. found that certain serum biomarkers, such as fasting glucose and triglycerides, were significantly associated with the presence of colonic polyps in this population. ¹³ These findings suggest that a panel of serum biomarkers could potentially serve as a non-invasive screening tool to identify acromegaly patients at higher risk for colonic neoplasia, although further research is needed to validate these findings and establish their clinical utility.

The optimal management of acromegaly necessitates early intervention. Transsphenoidal resection remains the treatment of choice for pituitary adenomas when feasible, as it offers the potential for long-term remission and biochemical control. ¹⁶

In the present case, the patient was appropriately referred for surgical consultation – a strategy supported by current guidelines and data from the ACROPRAXIS program demonstrating uniform management practices across clinical settings. ¹³ Given the well-documented benefits of early treatment on mitigating comorbidities such as cardiovascular disease, diabetes, and even gastrointestinal neoplasia, the case underscores the critical role of prompt diagnosis and intervention.

Recent compilations of data from international registries, including the LAS Database, have elucidated the risk profile for colonic lesions in acromegaly. The reported prevalence for colonic polyps stands at roughly 13%, while only a minor subset (approximately four patients in large cohorts) present with colorectal cancer at the time of diagnosis. ¹¹ Although the absolute risk of malignancy remains relatively low, these findings justify routine colonoscopic surveillance in patients with acromegaly, especially given the pro-proliferative actions of IGF‑1 on intestinal mucosa. ¹⁷

In our case, the giant size of the colonic polyp not only necessitated therapeutic resection due to its potential for malignant transformation but also proved to be an important clinical clue that precipitated the workup for acromegaly. This case thus adds to the growing body of evidence that endoscopic findings in acromegaly should prompt a thorough endocrine evaluation.

A review of the literature reveals several challenges in the timely diagnosis of acromegaly. ¹⁸ Click or tap here to enter text. The insidious onset of clinical manifestations often results in a delay of several years before a definitive diagnosis is made, as demonstrated in other case reports where diagnostic errors and delayed recognition led to complications such as unresectable tumors. ¹⁹ In the current case, early detection was facilitated by a concurrent gastroenterological evaluation, underscoring the importance of cross-disciplinary vigilance. Clinicians are thus encouraged to maintain a high index of suspicion for acromegaly when faced with inexplicable colonic findings, particularly in younger patients with subtle systemic signs.

Conclusion

This case illustrates a rare but important presentation of acromegaly, initially unmasked by a giant colonic polyp in a young male patient. It emphasizes the need for diagnostic vigilance, as subtle physical features may be overlooked without a high index of suspicion. Integration of gastrointestinal and endocrine evaluations is crucial for early recognition and coordinated management. Routine assessment of IGF-1 and GH levels in patients with atypical or large colonic lesions can facilitate the timely diagnosis of underlying endocrine disorders. Ultimately, a multidisciplinary approach enables effective treatment and improves patient outcomes.