Bronchial carcinoid tumors commonly present with pulmonary symptoms such as wheezing, hemoptysis, dyspnea or pneumonia. In infrequent cases, bronchial carcinoids may elaborate hormonally active products resulting in Cushing’s syndrome (2%) or carcinoid syndrome (2%). Acromegaly may also result if the tumor produces growth hormone (GH) or growth hormone releasing hormone (GHRH). Carcinoid tumors are responsible for <1% of acromegaly cases with only 50 being described in the literature and fewer than half in the setting of bronchial carcinoid (1).
A 44 year old man was referred to our institution by his primary care physician after a chest radiograph, obtained for evaluation of a productive cough, shortness of breath and lightheadedness, demonstrated a left infra-hilar mass. Chest computed tomography (CT) subsequently revealed a circumscribed, enhancing 3×3×2 cm mass centrally in the basal aspect of the left lower lobe. An octreotide scan was obtained for further characterization exhibiting intense uptake at the site of the mass lesion consistent with a neuroendocrine neoplasm such as carcinoid. Flexible bronchoscopy revealed an endobronchial, vascular lesion in the shared lateral and posterior basal segmental orifice of the left lower lobe. Cytology from brushings, washings and transbronchial needle aspiration were non-diagnostic.On direct questioning, the patient admitted several physical changes over the preceding 14 months including: coarsening of the facial features and an increase in hat and glove size. The patient denied any episodes of flushing, joint symptoms or gastrointestinal complaints. Magnetic resonance (MRI) evaluation of the sella turcica for pituitary adenoma showed no abnormality. The patient underwent left lower lobectomy via posterolateral thoracotomy. The postoperative course was uneventful. Pathological analysis of the specimen revealed a 2.8×2.1×1.6 cm mass consistent with a typical carcinoid tumor. Specific stains for growth hormone were negative. GH levels were 10.4 ng/dl [normal <10ng/dl] at the time of surgery and decreased to 0.1 ng/dl by 5 months post-operatively. Insulin-like growth factor-1 (IGF-1) was similarily elevated to 766 ng/dl (normal 86–220 ng/dl) at the time of resection and decreased to 336 ng/dl at 5 months. GHRH assays were not performed as this is not available at our institution. At 1-year follow-up, GH levels remained in the normal range (2.2 ng/dl) and IGF-1 was only slightly elevated (271 ng/dl). The patient reports no progression of his signs or symptoms of acromegaly. Repeat chest CT shows no evidence of recurrence.
Presentations of acromegaly stemming from ectopic secretions of either GH or GHRH, though described, are in fact quite rare. Bronchial carcinoids as the source have been implicated more commonly than tumors in other anatomic locations. One commonly seen feature in these patients is the presence of pituitary hyperplasia, especially in the setting of ectopic GHRH production. This finding was absent in our patient. Biswal et al reported a case of direct GH elaboration from a bronchial carcinoid, observing a similar decrement in GH and IGF-1 levels following resection (2); the only such report in the literature to date. We believe the mild increase in GH coupled with the extreme IGF-1 elevation and lack of pituitary hyperplasia in our patient may indicate tumor elaboration of a GH secretogogue with similar function, though structurally distinct enough to not stain for GH immunohistochemically. This would represent a new mechanism for the presentation of clinical acromegaly in bronchial carcinoid.
Acromegaly resulting from bronchial carcinoid tumors follows a variety of complex biochemical pathways. Complete surgical resection can lead to normalization of biochemical markers and the symptom complex in these patients.
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