ACTH-Producing Pituitary Tumors

The Treatment of Cushing's Disease

Cushing's disease (CD), or pituitary-dependent Cushing's syndrome, is a severe endocrine disease caused by a corticotroph pituitary tumor and associated with increased morbidity and mortality. The first-line treatment for CD is pituitary surgery, which is followed by disease remission in around 78% and relapse in around 13% of patients during the 10-year period after surgery, so that nearly one third of patients experience in the long-term a failure of surgery and require an additional second-line treatment. Patients with persistent or recurrent CD require additional treatments, including pituitary radiotherapy, adrenal surgery, and/or medical therapy. Pituitary radiotherapy is effective in controlling cortisol excess in a large percentage of patients, but it is associated with a considerable risk of hypopituitarism. Adrenal surgery is followed by a rapid and definitive control of cortisol excess in nearly all patients, but it induces adrenal insufficiency. Medical therapy has recently acquired a more important role compared to the past, due to the recent employment of novel compounds able to control cortisol secretion or action. Currently, medical therapy is used as a presurgical treatment, particularly for severe disease; or as postsurgical treatment, in cases of failure or incomplete surgical tumor resection; or as bridging therapy before, during, and after radiotherapy while waiting for disease control; or, in selected cases, as primary therapy, mainly when surgery is not an option. The adrenal-directed drug ketoconazole is the most commonly used drug, mainly because of its rapid action, whereas the glucocorticoid receptor antagonist, mifepristone, is highly effective in controlling clinical comorbidities, mainly glucose intolerance, thus being a useful treatment for CD when it is associated with diabetes mellitus. Pituitary-directed drugs have the advantage of acting at the site responsible for CD, the pituitary tumor. Among this group of drugs, the dopamine agonist cabergoline and the somatostatin analog pasireotide result in disease remission in a consistent subgroup of patients with CD. Recently, pasireotide has been approved for the treatment of CD when surgery has failed or when surgery is not an option, and mifepristone has been approved for the treatment of Cushing's syndrome when associated with impairment of glucose metabolism in case of the lack of a surgical indication. Recent experience suggests that the combination of different drugs may be able to control cortisol excess in a great majority of patients with CD.

Bilateral adrenalectomy for Cushing's disease

PURPOSE

Review the indications, outcomes, and consequences of bilateral adrenalectomy (BLA) in patients with Cushing's disease.

METHODS

A literature review was performed.

RESULTS

The primary therapy for Cushing's disease is surgery, with medical therapy and radiation therapy relegated to an adjuvant role. BLA is indicated in cases of persistent disease following pituitary surgery or in situations where rapid normalization of hypercortisolism is required. When performed via the laparoscopic approach, BLA is associated with a significantly reduced morbidity compared to the traditional, open approach. Following BLA, patients are at risk for adrenal crisis and the concern of Nelson's syndrome. However, BLA leads to a rapid resolution of the signs and symptoms of CS and leads to an improved long-term quality of life.

CONCLUSION

BLA should be considered in the treatment algorithm for patients with persistent CD after failed pituitary surgery, especially in patients who have severe consequences of hypercortisolism or desire pregnancy.

An approach to the evaluation and treatment of Cushing’s disease

Cushing's syndrome is an uncommon disorder involving dysregulation of the hypothalamic-pituitary-adrenal axis resulting in endogenous hypercortisolemia. It has multiple causes, but most commonly is due to hypersecretion of corticotropin from the pituitary gland, called Cushing's disease. The diagnosis of Cushing's syndrome remains a challenge to clinicians because routine hormonal assays can have significant overlap in pathological and normal states. We will review an approach to evaluating patients with suspected cortisol excess. We will also discuss treatment options and post-surgical assessment for those diagnosed with Cushing's disease.

Assessment of left ventricular functions by tissue Doppler echocardiography in patients with Cushing's disease

OBJECTIVE

To verify whether tissue Doppler imaging (TDI) could contribute to a better understanding of the natural history of cardiomyopathy in active Cushing's disease (CD), through its enhanced sensitivity to diastolic dysfunction, and identifying preliminary regional signs of systolic dysfunction before the appearance of clinical symptoms of cardiac pathologies.

METHODS

Eleven women with newly diagnosed CD and 32 control cases, purposely matched for gender, age, body mass index and co-incidental diseases were enrolled in this study. Echocardiographic examinations were assessed by conventional echocardiography and tissue Doppler imaging. The peak systolic velocity (S'm), early diastolic myocardial peak velocity (E'm), late diastolic myocardial peak velocity (A'm), isovolumic acceleration (IVA), myocardial pre-contraction time (PCT'm), myocardial contraction time (CT'm) and myocardial relaxation time (RT'm) were measured at septal and lateral mitral anulus.

RESULTS

In TDI, E'm and, E'm/A'm ratio were significantly lower, and PCT'm/CT'm ratio was higher, S'm, A'm, peak early diastole/E'm ratio, PCT'm, and isovolumetric myocardial relaxation time values were similar at lateral and septal anulus in patients with CD than controls (p>0.05). Lateral and septal anulus IVA were significantly lower in patients with CD than the control group (p<0.05). Correlation analysis showed that IVA time at lateral anulus correlated positively with S'm at lateral anulus (r=0.58; p=0.002) and IVA time at septal anulus correlated positively with S'm at septal anulus (r=0.51; p=0.008).

CONCLUSION

Our study confirms that patients with CD have impaired diastolic function. More importantly, we also demonstrated an impairment of myocardial systolic function in patients with CD by TDI. We recommend using TDI in addition to conventional echocardiography parameters for the cardiovascular risk assessment of patients with Cushing' syndrome.

Nelson syndrome: comprehensive review of pathophysiology, diagnosis, and management

Nelson syndrome (NS) is a rare clinical manifestation of an enlarging pituitary adenoma that can occur following bilateral adrenal gland removal performed for the treatment of Cushing disease. It is characterized by excess adreno-corticotropin secretion and hyperpigmentation of the skin and mucus membranes. The authors present a comprehensive review of the pathophysiology, diagnosis, and management of NS. Corticotroph adenomas in NS remain challenging tumors that can lead to significant rates of morbidity and mortality. A better understanding of the natural history of NS, advances in neurophysiology and neuroimaging, and growing experience with surgical intervention and radiation have expanded the repertoire of treatments. Currently available treatments include surgical, radiation, and medical therapy. Although the primary treatment for each tumor type may vary, it is important to consider all of the available options and select the one that is most appropriate for the individual case, particularly in cases of lesions resistant to intervention.

Long-term remission rates after pituitary surgery for Cushing's disease: the need for long-term surveillance

OBJECTIVE

There have been a few reports on long-term remission rates after apparent early remission following pituitary surgery in the management of Cushing's disease. An undetectable postoperative serum cortisol has been regarded as the result most likely to predict long-term remission. Our objective was to assess the relapse rates in patients who underwent transsphenoidal surgery in order to determine whether undetectable cortisol following surgery was predictive of long-term remission and whether it was possible to have long-term remission when early morning cortisol was measurable but not grossly elevated. Endocrinological factors associated with late relapse were also studied.

PATIENTS

We reviewed the long-term outcome in 63 patients who had pituitary surgery for the treatment of Cushing's disease between 1979 and 2000.

MEASUREMENTS

Case notes were reviewed and the current clinical and biochemical status assessed. Our usual practice was that early after the operation, an 08:00 h serum cortisol was measured 24 h after the last dose of hydrocortisone. This was followed by a formal low-dose dexamethasone suppression test. Current clinical status and recent 24-h urinary free cortisol values were used as an index of activity of the Cushing's disease. If there was evidence suggesting relapse, a low-dose dexamethasone suppression test was performed. In many patients, sequential collections of early morning urine specimens for urinary cortisol to creatinine ratio were also performed in an attempt to diagnose cyclical and intermittent forms of recurrent hypercortisolism. We did this if there was conflicting endocrine data, or if patients were slow to lose abnormal clinical features.

RESULTS

Mean age at diagnosis was 40.3 years (range 14-70 years). Mean follow-up up time was 9.6 years (range 1-21 years). Forty-five patients (9 males/36 females) achieved apparent remission immediately after surgery and were subsequently studied long term. Of these 45 patients, four have subsequently died while in remission from hypercortisolism. Ten of the remaining 41 patients have relapsed. Of those 10, six demonstrated definite cyclical cortisol secretion. Two of the 10 had undetectable basal serum cortisol levels in the immediate postoperative period. Thirty-one patients are still alive and in remission. Fourteen (45%) of the 31 who remained in remission had detectable serum cortisol levels (> 50 nmol/l) immediately postoperatively, and remain in remission after a mean of 8.8 years. Our relapse rate was therefore 10/45 (22%), after a mean follow-up time of 9.6 years, with mean time to relapse 5.3 years.

CONCLUSIONS

The overall remission rate of 56% (35/63) at 9.6 years follow-up is disappointing and merits some re-appraisal of the widely accepted principle that pituitary surgery must be the initial treatment of choice in pituitary-dependent Cushing's syndrome. Following pituitary surgery, careful ongoing expert endocrine assessment is mandatory as the incidence of relapse increases with time and also with increasing rigour of the endocrine evaluation. A significant number of our patients were shown to have relapsed with a cyclical form of hypercortisolism.

Fractionated proton beam irradiation of pituitary adenomas

PURPOSE

Various radiation techniques and modalities have been used to treat pituitary adenomas. This report details our experience with proton treatment of these tumors.

METHODS AND MATERIALS

Forty-seven patients with pituitary adenomas treated with protons, who had at least 6 months of follow-up, were included in this analysis. Forty-two patients underwent a prior surgical resection; 5 were treated with primary radiation. Approximately half the tumors were functional. The median dose was 54 cobalt-gray equivalent.

RESULTS

Tumor stabilization occurred in all 41 patients available for follow-up imaging; 10 patients had no residual tumor, and 3 had greater than 50% reduction in tumor size. Seventeen patients with functional adenomas had normalized or decreased hormone levels; progression occurred in 3 patients. Six patients have died; 2 deaths were attributed to functional progression. Complications included temporal lobe necrosis in 1 patient, new significant visual deficits in 3 patients, and incident hypopituitarism in 11 patients.

CONCLUSION

Fractionated conformal proton-beam irradiation achieved effective radiologic, endocrinological, and symptomatic control of pituitary adenomas. Significant morbidity was uncommon, with the exception of postradiation hypopituitarism, which we attribute in part to concomitant risk factors for hypopituitarism present in our patient population.

Management of Nelson's syndrome: observations in fifteen patients

OBJECTIVE

To analyse the results of different treatment modalities for Nelson's syndrome, which was defined as radiological evidence of a pituitary macroadenoma, fasting plasma ACTH levels of more than 200 pmol/l after stopping glucocorticoid substitution for at least 24 h in a patient who had undergone bilateral adrenalectomy for Cushing's disease.

DESIGN

The medical reports of all Nelson's patients known in our hospital were studied with regard to treatment modalities and result of treatment. Clinical remission of Nelson's syndrome was defined as a reduction of tumour size to a diameter of 10 mm or less and fasting plasma ACTH levels less than 200 pmol/l after stopping glucocorticoid substitution for at least 24 h.

PATIENTS

Fifteen women with Nelson's syndrome were studied. Bilateral adrenalectomy had been performed 1-29 years before Nelson's syndrome was diagnosed. Before adrenalectomy eight patients had undergone unsuccessful transsphenoidal pituitary surgery.

RESULTS

Eight patients were initially followed without surgical or radiotherapeutical intervention during 1-7 years. In seven of them, plasma ACTH levels and tumour volumes increased progressively during this rather short observation period, with development of extrasellar extension in four patients. In one of these patients, who was planned for elective pituitary surgery, massive pituitary haemorrhage occurred which was fatal despite emergency pituitary surgery. Elective pituitary surgery was performed in 11 patients, of whom three were operated twice. Clinical remission was documented in five patients in the first year after operation. In one patient postoperative MR-imaging revealed no residual tumour mass but the postoperative plasma ACTH level was still elevated. In another patient a residual intrasellar macroadenoma and an increased plasma ACTH level remained stable for 22 years. The remaining four patients received postoperative radiotherapy because of residual tumour masses. Of these patients, one had a clinical remission. In two others relatively small residual intrasellar tumour masses remain, with a fasting plasma ACTH level of more than 200 pmol/l in one of them. The fourth patient died of the consequences of progressive tumour growth. Radiotherapy was the only treatment in two patients and did not result in clinical remission. Tumour volumes and plasma ACTH levels at the time of diagnosis of Nelson's syndrome were positively correlated (r = + 0.61, P < 0.05). This correlation was stronger at the moment of decision of either pituitary surgery or radiotherapy (r = + 0.85, P < 0.001). At the end of the follow-up period the correlation between tumour volumes and plasma ACTH levels in the combined pituitary surgery and/or irradiation only group was + 0.77 (P < 0.001). In the pituitary surgery group tumour volumes before and after surgery were directly correlated (r = + 0.70, P < 0.05).

CONCLUSIONS

Our results demonstrate that pituitary surgery of Nelson's macroadenomas is more successful when Nelson's adenomas are relatively small. Pituitary surgery should be performed before extrasellar expansion of the tumour occurs in order to attain long lasting remissions. Pituitary irradiation should be performed postoperatively in all patients with residual tumour. Our data also illustrate that in patients with Nelson's syndrome, plasma ACTH levels can reliably be used as an indirect approximation for tumour volume.

Antisense oligonucleotide-induced inhibition of adrenocorticotropic hormone release from cultured human corticotrophs

OBJECT

Available therapies for Cushing's disease are often inadequate or involve the risk of significant morbidity. Accordingly, the need arises for the development of novel treatments, especially for cases caused by corticotroph hyperplasia, a condition difficult to treat using standard therapies. In this study, the authors investigated the use of phosphorothioate antisense oligonucleotides as a potential treatment for Cushing's disease.

METHODS

Corticotrophs, obtained from a patient with Cushing's disease in whom pathological findings showed multifocal areas of corticotroph adenoma and hyperplasia, were grown in tissue culture. By assessing cell viability and using immunoradiometric assay techniques, it was determined that these cells grew autonomously and secreted adrenocorticotropic hormone (ACTH) in vitro. A fully phosphorothioated antisense oligonucleotide was constructed to be complementary to the first 25 bp of the region coding for ACTH in exon 3 of the proopiomelanocortin precursor. After incubation of the corticotrophs with liposome-coated phosphorothioate antisense oligonucleotides, a greater than 90% decrease in ACTH release was noted on Days 3 and 6, compared with nonsense-treated controls (p < 0.05).

CONCLUSIONS

Antisense oligonucleotides may prove to be a useful adjunct in treating Cushing's disease by targeting one of its fundamental problems, ACTH hypersecretion.

Pituitary macroadenoma and Cushing's disease in pediatric patients: patient report and review of the literature

Cushing's syndrome in pediatric patients has been rarely reported and most of the cases are due to adrenal tumors. When the etiology is an ACTH-secreting pituitary adenoma, most often it is a microadenoma. We report on a 9 year-old girl with an ACTH-secreting macroadenoma, whose surgical removal through transsphenoidal approach was extremely difficult due to invasion of the cavernous sinus as well as adjacent structures. After two surgical approaches and stereotactic radiotherapy, she still suffers from the deleterious effects of hypercortisolism, especially marked osteoporosis with vertebral collapse, which interferes with her walking and causes excruciating pain. Two months after the radiotherapy, we still had doubts about the prognosis regarding the persistence of the hypercortisolism. From six months on, her general health started improving, she lost weight, the backache disappeared and her cortisol level returned to normal.

Beneficial gamma-knife radiosurgery in a patient with Nelson's syndrome

A 50-year-old female patient with Cushing's disease had undergone transsphenoidal removal of the pituitary adenoma and conventional radiotherapy in 1988. Since no remission was achieved, she underwent bilateral adrenalectomy in May 1989. During out-patient follow-up, she developed signs and symptoms due to invasive Adrenocorticotrophic hormone (ACTH)-producing macroadenoma (Nelson's syndrome) in 1994. ACTH levels at that time were 3400 ng/l. Near-total surgical resection of a 2.0 x 2.5 pituitary tumour which slightly extended laterally into the cavernous sinus was achieved by subfrontal approach in June 1994. However, she rapidly developed a recurrence of her complaints, with a visual field defect inferior-nasal of the left eye, and a second operation was carried out in November 1994. Culture of the tumour's cells revealed significant inhibition of ACTH production by bromocriptine. Adjuvant treatment with this drug therefore was started in November 1994. Because of the rapid recurrence it was decided to treat her with gamma-knife radiosurgery. The dose that was given in January 1995 was 12 Gy to the border and 40 Gy into the centre of the tumour. During a follow-up of more than 2 years, no recurrence, but even a minor reduction of tumour mass was observed by magnetic resonance imaging (MRI). Plasma ACTH levels decreased gradually to levels between 200 and 400 ng/l, and ophthalmologic complaints disappeared. It is concluded that gamma-knife radiosurgery may be a good alternative for patients with Nelson's syndrome who have rapidly recurring disease.

Pituitary corticotroph macrotumors. Diagnosis and treatment

Pituitary corticotroph macrotumors occur in 10% to 50% of dogs with PDH. Clinical signs may be only those of hypercortisolism or may include neurologic signs such as stupor, inappetance, circling, or pacing. Currently, CT and MRI are the only tests that can confirm the presence of a pituitary macrotumor in these patients. Results of endocrine testing are not significantly different from those of dogs with a microtumor. When a macroscopic pituitary tumor is identified in a dog with neurologic signs, or if a larger tumor is found in a dog even in the absence of neurologic signs, radiation therapy is currently the treatment of choice. Unfortunately, success rates with treatment are variable. A better response may be seen if the tumor is smaller and neurologic signs are minimal or absent at the time of treatment.

The effects of therapy with rifampicin and isoniazid on basic investigations for Cushing's syndrome

Rifampicin(R) is a potent enzyme inducer which is now widely used to treat many conditions. We have investigated its effect on adrenal function tests in 18 adults with tuberculosis on rifampicin (R) and isoniazid (INH) as in-patients. Midnight cortisol was above 250 nmol/l in 11 patients with a mean +/- (SD) of 340 +/- 193 nmol/l. The morning serum cortisol following 1 and 4 mg dexamethasone overnight was abnormal in 88.9 per cent and 83.3 per cent respectively. The respective mean values +/- (SD) were 350 +/- 179 and 336 +/- 279 nmol/l. The mean 24-hour urinary free cortisol +/- SD was 513 +/- 375 nmol and was above normal in 6 (33.3 per cent) patients. These results show that midnight cortisol, dexamethasone suppression tests and 24-hour urinary free cortisol are misleading in patients with tuberculosis on (R) and should not be employed for investigating such patients for Cushing's syndrome.

Is there a role for somatostatin and its analogs in Cushing's syndrome?

The effects of somatostatin and its analogs have been studied in different subclasses of patients with Cushing's syndrome (due to Cushing's disease, ectopic corticotropin [ACTH]- and/or corticotropin-releasing hormone [CRH]-secreting tumors, or ACTH-independent Cushing's syndrome) and in patients with Nelson's syndrome. In most patients with untreated Cushing's disease, octreotide does not suppress ACTH release, a finding that is supported by in vitro studies. However, octreotide or somatostatin inhibits pathological ACTH secretion in Nelson's syndrome. Short-term octreotide treatment has caused a significant initial response (decreased serum cortisol, ACTH, and cortisoluria) in 24 of 38 (64%) patients with ectopic ACTH/CRH Cushing's syndrome, and long-term treatment caused a persistent response in 10 of 14 (71%) cases. Pentetreotide scintigraphy may help to identify those patients with ectopic ACTH/CRH tumors who will have an initial response to octreotide, and is useful for locating ectopic ACTH/CRH-secreting tumors and their metastases. To date, octreotide has been shown to temporarily suppress gastric inhibitory peptide (GIP)-induced cortisol secretion in GIP-dependent (ACTH-independent) Cushing's syndrome, but has not shown any therapeutic benefit in other forms of ACTH-independent Cushing's syndrome.

Early diagnosis of Nelson's syndrome

Nelson's syndrome is a specific form of Cushing's disease treated by bilateral adrenalectomy, presenting with a deep hyperpigmentation caused by a pituitary adenoma (corticotropinoma). These ACTH-secreting tumors are frequently aggressive, so early diagnosis is of prime importance. We have studied 33 patients with Nelson's syndrome, 28 women and 5 men, aged 14-56 yr at the time of adrenalectomy and 16-58 yr at the time of Nelson's syndrome diagnosis (observed for 5-32 yr). Methods of examination included simultaneous adrenocorticotropic hormone (ACTH) and cortisol measurements during routine hydrocortisone replacement therapy, computed tomography (CT), pituitary magnetic resonance imaging (MRI), and visual field examination. The results obtained in a group of six patients diagnosed in the last 3 yr were compared with those obtained in a group of 27 patients examined before 1992. High plasma ACTH levels accompanied by normal serum cortisol concentration were characteristic for a late stage of the disease. Absolute temporal scotomas were an early finding. MRI, especially with the gadolinium enhancement, was superior to CT in demonstrating pituitary microadenomas in Nelson's syndrome. Thus, MRI diagnosis allowed for an early neurosurgical treatment of the patients with Nelson's tumors.

Failure of Partial Hypophysectomy as Definitive Treatment in Cushing's Disease Owing to Nodular Corticotrope Hyperplasia: Report of Four Cases

Nodular corticotrope hyperplasia is a rare pathology causing Cushing's syndrome owing to a primary pituitary disease or ectopic CRH production. In this study, we evaluated the laboratory and pathological findings and results of transsphenoidal pituitary surgery in four patients with Cushing's disease. Dynamic tests of pituitary-adrenal function (dexamethasone suppression, metyrapone, CRH, and DDAVP tests) were done before and after transsphenoidal pituitary surgery. Plasma and total urinary cortisol, serum 11-deoxycortisol, and plasma ACTH were determined by RIA. Hormonal dynamic tests and radiologic studies were compatible with a pituitary ACTH source. The transsphenoidal surgery revealed the presence of corticotrope hyperplasia confirmed by immunoperoxidase stain and a preserved reticulum framework in the removed pituitary tissue of these four patients. The pituitary surgery led to a short period of improvement in two of the patients (1 and 4), a 3-yr remission in one patient (patient 2), and no improvement in one (patient 3). We conclude that although our patients appear to have inadequate suppression with high-dose dexamethasone, there is no way to diagnose this pathology presurgically, and that total hypophysectomy, bilateral adrenalectomy, and irradiation are the only alternatives for definitive treatment. A CRH-secreting ectopic tumor could not be found in our patients either before or after surgery in the follow-up period.

Morbidity and mortality in Cushing's disease: an epidemiological approach

OBJECTIVE

Although Cushing's disease is a well documented clinical entity, there is no epidemiological information about it. The present study tries to obtain this information.

DESIGN AND PATIENTS

Forty-nine patients affected by Cushing's disease living in Vizcaya (Spain) between 1975 and 1992 were considered for an epidemiological study.

RESULTS

The prevalence of known cases at the end of 1992 was 39.1 per million inhabitants. The average incidence of newly diagnosed cases was 2.4 cases per million people per year. Cushing's disease was more frequent in women (n = 46) than in men (n = 3), with a ratio of 15:1. Diabetes mellitus and hypertension were observed in 38.7 and 55.1% of patients, respectively. Remission of Cushing's disease was achieved in 36 out of 41 patients (87.5%). In general, the mortality was higher than that expected for the control population (standardized mortality ratio, SMR 3.8, 95% confidence interval, CI 2.5-17.9, P < 0.03). Concerning the cause of death, the SMR of vascular disease was 5 (95% CI 3.4-48.6, P < 0.05). Higher age, persistence of hypertension and abnormalities of glucose metabolism after treatment, were independent predictors of mortality (multivariate analyses, P < 0.01).

CONCLUSIONS

Prevalence of Cushing's disease was 39.1 cases/million inhabitants and average incidence was 2.4 cases/million per year. Mortality was elevated, due to vascular disease, associated with higher age, persistence of hypertension and impaired glucose metabolism.

Corticotroph (Basophil) invasion of the pars nervosa in the human pituitary: Localization of proopiomelanocortin peptides, galanin and peptidylglycine α-amidating monooxygenase-like immunoreactivities

Corticotroph (basophil) invasion or the migration of corticotroph cells into the pars nervosa of the human pituitary gland was found in 35 of 767 (4.4%) consecutive pituitaries obtained at autopsy. The degree of invasion increased with patient age and extensive invasion was more common in men than in women. Immunoreactive ACTH, β-MSH, α-MSH, and galanin were detected both in the anterior lobe and invading corticotroph cells in approximately equal frequency. Fewer cells stained positively for α-MSH than for the three other peptides in both the anterior lobe and invading corticotrophs. Twelve corticotropic pituitary adenomas obtained surgically from patients with Cushing's disease were also examined and expressed varying degrees of immunoreactivity for ACTH, α MSH, β-MSH and galanin. Staining for all major pituitary hormones revealed only ACTH in the invading basophil cells. Peptidylglycine α-amidating monooxygenase (PAM) was present in the anterior pituitary, in invading corticotroph cells, and in some cells lining the cysts of the pars intermedia zone. PAM immunoreactivity was also detected in 4/12 corticotroph adenomas. These results indicate that corticotroph cells invading the pars nervosa are immunohistochemically similar to anterior lobe corticotrophs and have the ability to amidate various peptides such as proopiomelanocortin cleavage products and galanin with PAM.