Ectopic Growth Hormone-releasing Hormone Secretion Research Articles

SUN-930 A Case of Acromegaly Secondary to Ectopic Growth Hormone-Releasing Hormone (GHRH) Secretion from a Bronchial Neuroendocrine Tumour

A Case of Acromegaly Secondary to Ectopic Growth Hormone-Releasing Hormone (GHRH) Secretion from a Bronchial Neuroendocrine TumourBackgroundAcromegaly due to ectopic GHRH secretion is a rare disorder and only accounts for less than 1% of all cases of acromegaly.CaseWe present the case of a 42-year old female with acromegaly from a bronchial neuroendocrine tumour (NET) secreting GHRH. The patient presented with gradual onset of dyspnea and wheezing. Subsequent imaging (chest X-ray, CT chest) revealed a large left-sided thoracic mass. Bronchoscopy was performed and a biopsy was taken from the mass. Initial histological examination reported small cell lung carcinoma (SCLC). Therefore, she underwent chemoradiotherapy. The patient was concurrently experiencing increased digital girth, weight gain, and enlarged tongue and was therefore referred to our endocrinology clinic for evaluation of acromegaly. Investigations revealed normal ACTH, markedly elevated IGF-1 (1031 μg/L, normal 63–215 μg/L), and non-suppressed GH levels following a 75g oral glucose tolerance test. The remainder of the pituitary panel, including TSH, prolactin, FSH, LH were all normal. An MRI sella showed a completely normal pituitary and pineal gland with no evidence of brain metastasis. She thus met clinical and biochemical criteria for acromegaly but a pituitary source could not be identified. Given her history, a paraneoplastic process or ectopic GHRH-producing tumour was suspected. Further workup showed a significantly elevated circulating GHRH levels of 73 pg/mL (normal 5 – 18 pg/mL). Subsequently, a second pathologist with expertise in NETs reviewed the same biopsy specimen. The specimen was found to be a GHRH-producing well differentiated pulmonary NET with a Ki67 index of 1.5%, and thus not a SCLC. Furthermore, a somatostatin receptor scintigraphy study was done which showed evidence of a somatostatin avid receptor rich lesion in the lung, corresponding to the known tumour. Thus, what initially appeared to be a SCLC was subsequently found to be a GHRH-secreting NET, illustrating the challenges of diagnosing these rare tumours. She was treated with intramuscular sandostatin 20mg q28days and then underwent a left pneumonectomy, resulting in biochemical resolution of her acromegaly (IGF-1 219 μg/L). Genetic testing for MEN1 was also completed as there is an association between ectopic GHRH NETs and MEN-1; however, genetic testing revealed no pathogenic variants and exon deletions or duplications suggestive of MEN-1.Learning pointsDiagnosis of acromegaly due to ectopic GHRH secretion requires high clinical suspicion by the treating clinicians (e.g., endocrinologist, oncologist) as well as review of histology by expert pathologists. Our case highlights that ectopic GHRH secretion is a rare but important cause of acromegaly, which should always be suspected when a clear pituitary cause is not identified.

Diagnostic challenges and management of a patient with acromegaly due to ectopic growth hormone-releasing hormone secretion from a bronchial carcinoid tumour.

SummaryA male patient presented at the age of 30 with classic clinical features of acromegaly and was found to have elevated growth hormone levels, not suppressing during an oral glucose tolerance test. His acromegaly was originally considered to be of pituitary origin, based on a CT scan, which was interpreted as showing a pituitary macroadenoma. Despite two trans-sphenoidal surgeries, cranial radiotherapy and periods of treatment with bromocriptine and octreotide, his acromegaly remained active clinically and biochemically. A lung mass was discovered incidentally on a chest X-ray performed as part of a routine pre-assessment for spinal surgery 5 years following the initial presentation. This was confirmed to be a bronchial carcinoid tumour, which was strongly positive for growth hormone-releasing hormone (GHRH) and somatostatin receptor type 2 by immunohistochemistry. The re-examination of the pituitary specimens asserted the diagnosis of pituitary GH hyperplasia. Complete resolution of the patient’s acromegaly was achieved following right lower and middle lobectomy. Seventeen years following the successful resection of the bronchial carcinoid tumour the patient remains under annual endocrine follow-up for monitoring of the hypopituitarism he developed after the original interventions to his pituitary gland, while there has been no evidence of active acromegaly or recurrence of the carcinoid tumour. Ectopic acromegaly is extremely rare, accounting for <1% of all cases of acromegaly. Our case highlights the diagnostic challenges differentiating between ectopic acromegaly and acromegaly of pituitary origin and emphasises the importance of avoiding unnecessary pituitary surgery and radiotherapy. The role of laboratory investigations, imaging and histology as diagnostic tools is discussed.Learning points:Ectopic acromegaly is rare, accounting for less than 1% of all cases of acromegaly.Ectopic acromegaly is almost always due to extra-pituitary GHRH secretion, mainly from neuroendocrine tumours of pancreatic or bronchial origin.Differentiating between acromegaly of pituitary origin and ectopic acromegaly can cause diagnostic challenges due to similarities in clinical presentation and biochemistry.Serum GHRH can be a useful diagnostic tool to diagnose ectopic acromegaly.Pituitary imaging is crucial to differentiate between a pituitary adenoma and pituitary hyperplasia, which is a common finding in ectopic acromegaly.Diagnosing ectopic acromegaly is pivotal to avoid unnecessary interventions to the pituitary and preserve normal pituitary function.

English

Ectopic growth hormone releasing hormone (GHRH) secretion is a rare cause of acromegaly and accounts for &lt;1% of cases. It is most commonly secondary to gastropancreatic neuroendocrine tumours and bronchial carcinoid tumours. We report a case of 57 years old man with adrenal phaeochromocytoma and acromegaly due to ectopic GHRH secretion in a patient with neurofibromatosis type 1. He presented with headache, sweating and newly diagnosed diabetes. The diagnosis was of acromegaly and pheochromocytoma was confirmed on investigations and imaging. Surgical removal of the pheochromocytoma in this case resulted in resolution of his diabetes, normalisation of his IGF-1 with adequate GH suppression on oral glucose tolerance test (OGTT) and regression of enlarged pituitary on postoperative magnetic resonance imaging (MRI) scan. To our knowledge, this is the first case of acromegaly associated with pheochromocytoma due to ectopic GHRH in a patient of neurofibromatosis in literature. Key words: Growth hormone releasing hormone (GHRH), pheochromocytoma, acromegaly, somatotrophs, neurofibromatosis.

Hirsutismus und Struma multinodosa bei einer 40-jährigen Uhrmacherin

This article presents the case of a female patient with acromegaly caused by ectopic production of growth hormone-releasing hormone (GHRH) secretion. In the presence of typical clinical features of acromegaly but a lack of evidence for a pituitary adenoma the results of somatostatin receptor scintigraphy were indicative of a typical carcinoid of the lungs as the cause of the ectopic secretion of GHRH and the stimulation of pituitary gland growth hormone secretion resulting in acromegaly. Finally, the patient underwent curative surgical treatment.

Growth hormone-releasing hormone-producing pancreatic neuroendocrine tumor in a multiple endocrine neoplasia type 1 family with an uncommon phenotype

The objective of this study was to describe a multiple endocrine neoplasia type 1 (MEN1) family characterized by primary hyperparathyroidism, in association with acromegaly because of ectopic growth hormone-releasing hormone (GHRH) secretion by a pancreatic neuroendocrine tumor in a young man and with a bronchial carcinoid in his mother. We investigate the clinical, radiological imaging, histopathologic findings, and therapy. An 18-year-old man successfully underwent subtotal parathyroidectomy for primary hyperparathyroidism. A subsequent genetic analysis showed a MEN1 gene mutation. Three years later, acromegaly because of ectopic GHRH secretion was diagnosed (pituitary MRI negative and elevated GHRH levels). A search for an ectopic tumor was unsuccessful and somatostatin analog therapy was started. Successively, scintigraphy with somatostatin analogs (68-Ga-DOTATOC-PET) showed three focal areas in the pancreatic tail. Distal pancreatectomy showed multiple pancreatic neuroendocrine tumors and hormonal status was normalized. Afterwards, the evaluation of the patient's mother, carrying the same mutation, indicated a primary hyperparathyroidism and a 4 cm lung mass. The patient underwent subtotal pneumonectomy and the histological analysis was consistent with the diagnosis of a typical bronchial carcinoid. In conclusion, an atypical phenotype may be recorded in MEN1 families, thus emphasizing the importance of the new imaging and surgical techniques in the diagnosis and treatment of such a rare disease.

A Case of Ectopic Growth Hormone Releasing Hormone (GHRH) from Pancreatic Neuroendocrine Tumor Resistant to Therapy

Introduction: Ectopic secretion of GHRH is a rare cause of acromegaly. However, its recognition is clinically important because different therapeutic approaches are required. Case Presentation: We present a challenging case of acromegaly secondary to ectopic GHRH secretion from pancreatic neuroendocrine tumor in a 52-year-old female. The patient is treated with different modalities which include pegvisomant in an attempt to control the stimulated GH-axis considering the limited data about its use in treatment of ectopic acromegaly. Conclusion: GHRH-secreting tumor is a rare cause of acromegaly. Surgical resection of the tumor is the therapy of choice whenever possible. However, further studies are warranted for unresectable tumor or resistant cases.

Acromegaly induced by ectopic secretion of GHRH: A review 30 years after GHRH discovery

Ectopic acromegaly is very rare and since the discovery of growth hormone-releasing hormone (GHRH), 30 years ago, only 74 cases have been reported in the literature. Except for a recent French series of 21 cases, most of them were case reports. The present review summarizes the current knowledge on clinical presentation, diagnosis and prognosis. Tumors secreting GHRH are neuroendocrine tumors, usually well differentiated and mainly from pancreatic or bronchial origin. They are usually large and easy to localize using TDM and somatostatin receptor scintigraphy. Clinical presentation is an acromegaly of variable intensity, whose features are similar to that of a somatotropic adenoma. Pituitary may be normal or enlarged at MRI which may be difficult to interpret especially in MEN1 patients where the association of a microprolactinoma to a pancreatic tumor secreting GHRH may be misleading. GHRH plasmatic measurement has an excellent specificity for the diagnosis, using a threshold of 250 to 300ng/L and is a good tool for follow-up of patients after treatment. These tumors have a good overall prognosis, even in metastatic forms which represent 50% of cases. Surgical approach is recommended and, when a complete tumoral resection is feasible, results, in most patients, in long-lasting remission. In such cases, GHRH concentration is normalized and its increase is an accurate indicator of recurrence. In uncured patients, somatostatin analogs control GH secretion but inhibit, only partially, GHRH secretion. MEN1 mutation should be systematically investigated in patients with a pancreatic tumor.

Ectopic acromegaly due to growth hormone releasing hormone

Acromegaly secondary to extra-pituitary tumors secreting growth hormone releasing hormone (GHRH) is rarely encountered. We review the literature on ectopic acromegaly and present the index report of ectopic acromegaly secondary to GHRH secretion from a mediastinal paraganglioma. Clinical and pathological manifestations and therapeutic management of 99 patients with ectopic acromegaly are reviewed. Acromegaly secondary to ectopic GHRH secretion is usually caused by a neuroendocrine tumor in the lung and pancreas. We report an additional cause of ectopic acromegaly from a mediastinal paraganglioma. Diagnostic criteria of ectopic GHRH syndrome include biochemical and pathologic tumoral confirmation of GHRH secretion and expression. Management of ectopic acromegaly consists of surgical resection of the primary tumor and biochemical normalization, with possible adjuvant use of somatostatin analogs. The review demonstrates that there are several tumor types, including paragangliomas which may secrete GHRH, leading to acromegaly. Clinical and laboratory manifestations of the syndrome and challenges in diagnosis and management of these rarely encountered patients require early diagnosis and appropriate treatment to prevent long-term morbidity and mortality with ectopic acromegaly.

Clinical Characteristics and Outcome of Acromegaly Induced by Ectopic Secretion of Growth Hormone-Releasing Hormone (GHRH): A French Nationwide Series of 21 Cases

Ectopic GHRH secretion is a rare cause of acromegaly, and case reports are mainly isolated. From the registry of the sole laboratory performing plasma GHRH assays in France, we identified cases of ectopic GHRH secretion presenting with acromegaly between 1983 and 2008. Twenty-one patients aged 14-77 yr were identified from 12 French hospitals. Median GHRH was 548 (270-9779) ng/liter. Outcome measures included description of tumor features and outcome and the relation between plasma GHRH values and tumor site, size, and spread. The primary neuroendocrine tumor was identified for 20 of 21 patients (12 pancreatic, seven bronchial, one appendicular). Tumors were large (10-80 mm), identified on computed tomography scan in 18 cases and by endoscopic ultrasound and somatostatin receptor scintigraphy in two. Somatostatin receptor scintigraphy had a similar sensitivity to computed tomography scan (81 vs. 86%). Tumors were all well differentiated; 47.6% had metastasized at the time of diagnosis of acromegaly. After a median follow-up of 5 yr, 85% of patients were alive. Ninety-one percent of patients whose tumor was completely removed were considered in remission, and most had normalized plasma GHRH. The remaining patients were treated with somatostatin analogs: IGF-I normalized except for one patient who required pegvisomant, but GHRH levels remained elevated. No correlations were found between GHRH levels and tumor site or size or the existence of metastases. Identification of increased plasma GHRH during follow-up was an accurate indicator of recurrence. The prognosis of endocrine tumors responsible for GHRH secretion appears relatively good. Plasma GHRH assay is an accurate tool for diagnosis and follow-up.

Ectopic secretion of GHRH by a pancreatic neuroendocrine tumor associated with an empty sella

Acromegaly is usually the result of a pituitary growth hormone cell-adenoma or is more rarely due to ectopic secretion of growth hormone releasing hormone (GHRH).We report the case of a 60-year-old woman with acromegaly due to a GH-RH-secreting pancreatic tumor. Laboratory evaluation confirmed the diagnosis of acromegaly. Magnetic resonance imaging revealed a partial empty sella with no signs of adenoma. Ultrasound sonography performed for abdominal pains showed a calcified large heterogeneous infrahepatic mass. Computed tomography scan discovered a heterogeneous pancreatic head mass with a diameter of 10 cm. Measurement of fasting plasma GHRH was performed showing a high concentration of 604 ng/L (normal 10–60). We therefore concluded that the acromegaly was caused by ectopic overproduction of GHRH likely due to the pancreatic tumor. The patient underwent a cephalic duodenopancreatectomy. Histology revealed a well-circumscribed tumor with organoid architecture. Immunohistochemistry demonstrated diffuse positivity for chromogranin A, neuronal specific enolase and synaptophysin and negative immunoreactivity for prolactin, GH and serotonin. These features were concordant with a well-differentiated neuroendocrine tumor of the pancreas. Surgical resection of this pancreatic tumor was followed by significant amelioration of acromegalic signs and normalization of GHRH and GH levels.

Ectopic growth hormone-releasing hormone secretion by a bronchial carcinoid tumor: clinical experience following tumor resection and long-acting octreotide therapy

Acromegaly resulting from the ectopic secretion of growth hormone-releasing hormone (GHRH) is rare. We present a case of acromegaly secondary to proven GHRH-secretion by a bronchial carcinoid tumor in a type 1 diabetic subject and document the clinical course pre- and post-resection of the tumor and of subsequent octreotide therapy. A 54-year-old Caucasian man was referred for evaluation of acromegalic symptoms and significantly increased insulin requirements. He had a history of left lung surgery 20 years prior for hemoptysis. Initial laboratory results indicated acromegaly. Fasting serum growth hormone (GH): 26.1 ng/mL (0-5 ng/mL), insulin-like growth factor 1 (IGF-1): 635 ng/mL (87-283 ng/mL), GH at 60 min post-ingestion of 75 grams of oral glucose during a glucose tolerance test: 8.3 ng/mL (normal <1 ng/mL). Pituitary magnetic resonance imaging (MRI) revealed diffuse pituitary enlargement without adenoma. A 4.4 cm left hilar mass was noted on chest computed tomography (CT) scan. Further evaluation for a suspected GHRH-secreting neuroendocrine tumor was pursued. Plasma GHRH level was elevated: 198 pg/mL (<50 pg/mL). Octreoscan showed radiolabelled-octreotide uptake in the left lung mass and pituitary gland. Surgical resection of the lung mass was performed. Immunohistochemical study of the tumor tissue indicated a neuroendocrine tumor secreting GHRH. Postoperatively, serum GHRH, GH and IGF-1 levels fell precipitously. At 10 months, IGF-1 levels were mildly elevated and 7 months of 10 mg long-acting octreotide therapy (Sandostatin(®) LAR(®)) was trialed. At 20 months, off octreotide, serum IGF-1 levels had normalized, acromegalic features were receding, and the patient's daily insulin requirements had decreased by 57%.

Ectopic Growth Hormone-Releasing Hormone Secretion by a Neuroendocrine Tumor Causing Acromegaly: Long-Term Follow-Up Results

Ectopic secretion of growth hormone-releasing-hormone (GHRH) is a rare cause of acromegaly-representing less than 1% of patients. A 25-year-old woman was admitted to the hospital with acromegaly and a 6 x 6 cm infrahepatic mass. Sellar magnetic resonance imaging indicated diffuse pituitary enlargement consistent with hyperplasia. The infrahepatic mass was resected, and the histopathological diagnosis was a well-differentiated invasive neuroendocrine carcinoma of the duodenum with metastases to local lymph nodes. The tumor cells contained cytoplasmic immunoreactivity for GHRH. Because increased IGF-1 concentrations persisted after the operation, the patient was treated with octreotide long-acting repeatable (LAR) injections of 20 mg/month. Growth hormone and IGF-1 levels normalized. After 6 years of surveillance, a left paraaortic mass was detected by uptake of indium 111 octreotide. Surgical exploration revealed metastatic neuroendocrine carcinoma in a 2.5-cm lymph node. Postoperatively, the IGF-1 concentration was mildly elevated. Octreotide LAR therapy is being continued at 10 mg/month. This case suggests that octreotide treatment may have a beneficial effect on disease course and can be maintained for as long as 7 years in a patient with acromegaly due to a GHRH-secreting neuroendocrine carcinoma.

The Discovery of Growth Hormone‐Releasing Hormone1: An Update

The Discovery of Growth Hormone‐Releasing Hormone¹: An Update

Acromegaly Secondary to Growth Hormone-releasing Hormone Secreted by an Incidentally Discovered Pheochromocytoma

Ectopic growth hormone-releasing hormone (GHRH)-secreting tumors are rare and cause acromegaly with somatotroph hyperplasia. We report a case of acromegaly secondary to GHRH secretion by an incidentally discovered pheochromocytoma in a normotensive patient. A 23-year-old man presented with signs and symptoms of acromegaly. Laboratory evaluation confirmed the diagnosis and magnetic resonance imaging (MRI) revealed a sellar mass which was thought to be a macroadenoma and surgically resected. The patient was not cured and medical treatment was indicated. An abdominal ultrasound performed before initiation of medical treatment showed a solid/cystic lesion superiorly to the right kidney. An abdominal MRI confirmed an adrenal tumor. Hormonal workup of the adrenal incidentaloma revealed elevated urinary catecholamine and total metanephrines findings strongly suggestive of a pheochromocytoma. Acromegaly was then suspected to be due to ectopic secretion of GHRH by the tumor. Patient underwent surgical resection and histopathologic examination confirmed a pheochromocytoma which stained positively for GHRH. Also, review of the pituitary specimen confirmed somatotrophic hyperplasia. Genetic analysis of the ret proto-oncogene showed no mutation. Pituitary MRI was repeated 10 months after pheochromocytoma resection and revealed a slightly enlarged pituitary and partial empty sella. The diagnosis of acromegaly caused by ectopic production of GHRH is a challenging task. A careful histopathological examination of the surgically excised pituitary tissue has a key role to arouse the suspicion and guide the investigation of a secondary cause of acromegaly.

Ectopic growth hormone-releasing hormone secretion by a metastatic bronchial carcinoid tumor: a case with a non hypophysial intracranial tumor that shrank during long acting octreotide treatment

Ectopic acromegaly represents less than 1% of the reported cases of acromegaly. Although clinical improvement is common after treatment with somatostatin (SMS) analogs, the biochemical response and tumor size of the growth hormone-releasing hormone (GHRH)-producing tumor and its metastases are less predictable. Subject A 36-year-old male was referred because of a 3-year history of acromegaly related symptoms. He had undergone lung surgery in 1987 for a "benign" carcinoid tumor. Endocrine evaluation confirmed acromegaly Plasma IGF-1: 984 ng/ml (63-380), GH: 49.8 ng/ml (<5). MRI showed a large mass in the left cerebellopontine angle and diffuse pituitary hyperplasia. Pulmonary, liver and bone metastases were shown by chest and abdominal CT scans. Ectopic GHRH secretion was suspected. Methods Measurement of circulating GHRH levels by fluorescence immunoassay levels and immunohistochemical study of the primary lung tumor and metastatic tissue with anti-GHRH and anti-somatostatin receptor type 2 (sst2A) antibodies. Results Basal plasma GHRH: 4654 pg/ml (<100). Pathological study of liver and bone biopsy material and lung tissue removed 19 years earlier was consistent with an atypical carcinoid producing GHRH and exhibiting sst2A receptor expression. Treatment with octreotide LAR 20-40 mg q. month resulted in normalization of plasma IGF-1 levels. Circulating GHRH levels decreased dramatically. The size of the left prepontine cistern mass, with SMS receptors shown by a radiolabeled pentetreotide scan, decreased by 80% after 18 months of therapy. Total regression of pituitary enlargement was also observed. No changes were observed in lung and liver metastases. After 24 months of therapy the patient is asymptomatic and living a full and active life.

Update in pulmonary carcinoid tumors: a review article.

Pulmonary carcinoid tumors are neuroendocrine malignant tumors that make up 1% to 2% of all lung tumors. According to histopathologic criteria, carcinoids can be divided into typical (TC) and atypical (AC) carcinoids. Carcinoids can be placed in a spectrum of neuroendocrine tumors, ranging from low-grade malignant TC to intermediate AC to high-grade large-cell neuroendocrine carcinoma and small-cell lung carcinoma. Familial pulmonary carcinoids are rare. The most common symptoms are hemoptysis, cough, recurrent pulmonary infection, fever, chest discomfort and chest pain, unilateral wheezing, and shortness of breath. Paraneoplastic syndromes are rare and include carcinoid syndrome, Cushing's syndrome, and ectopic growth hormone-releasing hormone secretion. The diagnosis is usually established by flexible bronchoscopy and biopsy, although occasionally this can result in severe hemorrhage. Immunoscintigraphy by somatostatin analogs can also be useful in diagnosis. The treatment of choice is surgical resection, and prognosis is relatively good in TC, although it is worse in AC. The role of radiotherapy and chemotherapy as part of multimodality treatment or palliation is still debated.

Acromegaly caused by ectopic growth hormone-releasinghormone secretion

Acromegaly caused by ectopic growth hormone-releasinghormone secretion

Acromegaly due to ectopic growth hormone-releasing hormone secretion by a bronchial carcinoid tumour. Dynamic hormonal responses to various stimuli : Glikson M, Gil-Ad I, Galun E, Dresner R, Zilberman S, Halperin Y et al. Heart Institute, Chaim Sheba Medical Centre, Tel'Hashomer IL-52621. Acta Endocrinol 1991;125:366–71

Acromegaly due to ectopic growth hormone-releasing hormone secretion by a bronchial carcinoid tumour. Dynamic hormonal responses to various stimuli : Glikson M, Gil-Ad I, Galun E, Dresner R, Zilberman S, Halperin Y et al. Heart Institute, Chaim Sheba Medical Centre, Tel'Hashomer IL-52621. Acta Endocrinol 1991;125:366–71

Acromegaly due to ectopic growth hormone-releasing hormone secretion by a bronchial carcinoid tumour. Dynamic hormonal responses to various stimuli

Ectopic GHRH is a relatively uncommon cause of acromegaly, which should be differentiated from pituitary adenoma, in order to avoid damage to the pituitary gland from unnecessary interventions. We report here on a 66-year-old man with acromegaly due to a GHRH-secreting bronchial carcinoid tumour, who recovered completely following removal of the tumour. His hormonal status was studied before and after the operation. Basal GH, GHRH, IGF-I and PRL levels, as well as plasma GH response to glucose load and TRH administration were abnormal before the operation, and became normal thereafter. The somatostatin analogue SMS 201-995 was found to be a potent inhibitor of the ectopic GHRH and the GH secretion (greater than 500 to 42 ng/l and 15.4 micrograms/l to 0.8 microgram/l, respectively). The effect on GHRH proved to be due to direct effect of somatostatin on the tumour cells, as demonstrated in tissue culture studies. A mixed meal was found immediately to suppress GHRH levels without such an effect on GH secretion. We conclude that the neuroendocrine tests usually practised in acromegaly cannot differentiate between ectopic GHRH secretion and pituitary adenoma. High plasma GHRH levels may serve as a diagnostic test for excessive GHRH production, which is almost always ectopic. These high levels are suppressible by somatostatin and a mixed meal.