Somatostatin regulation of glycoprotein hormone and free subunit secretion in clinically nonfunctioning and somatotroph adenomas in vitro.

There is increasing evidence that clinically nonfunctioning pituitary tumors produce and secrete glycoprotein hormone and/or free alpha- and beta-subunits. In addition, hypersecretion of free alpha-subunit occurs in up to 37% of patients with somatotroph adenomas. An understanding of glycoprotein hormone regulation is important in developing effective therapeutic strategies for patients with tumors associated with intact glycoprotein hormone and free subunit hypersecretion. We investigated glycoprotein hormone and free subunit secretion by somatostatin in primary dispersed cultures of pituitary tumor cells from 23 patients with pituitary adenomas. Fifteen tumors from patients with clinically nonfunctioning adenomas (group 1) and 8 tumors from patients with somatotroph adenomas and cosecretion of alpha-subunit (group 2) were studied. Cultures were incubated with control or somatostatin-supplemented media for 24 h. Media samples from group 1 tumors were assayed for intact glycoprotein hormones and free alpha- and beta-subunits secretion levels, while media samples from group 2 cultures were assayed for alpha-subunit and GH secretion levels. Significant (P less than 0.05-0.001) inhibition of secretion of 1 or more intact hormones and/or free subunits was found in 10 of the 15 group 1 tumors. SRIF[10(-7) M] suppressed intact gonadotropin secretion in 60% of FSH-producing tumors and 30% of LH-producing tumors. Media concentrations of FSH beta and LH beta were decreased in 31% and 50% of group 1 tumors, respectively, following somatostatin treatment in those tumors which secreted free beta-subunits. alpha-Subunit was secreted by 12 of the 15 tumors, but significant (P less than 0.02-0.01) inhibition by somatostatin was observed in only 2 tumors. In contrast, significant (P less than 0.05-0.001) inhibition of alpha-subunit in the somatotroph adenomas was found in 6 of the 8 tumors. Significant decreases in alpha-subunit were observed only in those tumors where GH was also significantly inhibited by somatostatin. We conclude that 1) somatostatin inhibits intact glycoprotein or free subunit secretion in the majority of clinically nonfunctioning pituitary tumors in vitro and 2) alpha-subunit secretion is suppressed in 17% and 69% of clinically nonfunctioning and somatotroph adenomas, respectively, consistent with a differential regulation of alpha-subunit by somatostatin in these two tumor types.     

Serum alpha-subunit levels in patients with pituitary adenomas

OBJECTIVE: We investigated preoperative and postoperative serum alpha-subunit levels and the alpha-subunit response to TRH in patients with various types of pituitary tumour and correlated the data with histological findings in order to clarify the significance of alpha-subunit measurement in pituitary adenomas. PATIENTS: We examined 59 patients with pituitary tumours (22 with GH cell adenomas, 30 with clinically nonfunctioning adenomas and seven with other tumours) treated at Toranomon Hospital between 1996 and 1998. RESULTS: The basal alpha-subunit level was supranormal in six out of 22 (27%) patients with a GH cell adenoma and in nine out of 30 (30%) patients with a nonfunctioning adenoma. A paradoxical alpha-subunit response to TRH was found in seven out of 22 (32%) patients with a GH cell adenoma. These seven patients also showed a paradoxical GH response to TRH administration. In addition, paradoxical response to TRH was found in eight out of 30 (27%) patients with a clinically nonfunctioning adenoma. In contrast, patients with other types of pituitary tumour showed neither a supranormal alpha-subunit level nor a paradoxical response to TRH. The supranormal alpha-subunit level and the abnormal response to TRH were normalized in both GH cell adenoma and nonfunctioning adenoma patients after successful surgery. Immunohistochemical studies showed alpha-subunit positive cells in 51% of GH cell adenomas or nonfunctioning adenomas and there was a good concordance with the serum alpha-subunit levels in both GH cell adenoma and nonfunctioning adenoma patients. CONCLUSIONS: These findings suggest that supranormal serum alpha-subunit levels are mainly due to hypersecretion by the tumour itself, while the paradoxical alpha-subunit response to TRH is an associated phenomenon in patients with a GH cell adenoma or nonfunctioning adenoma. The alpha-subunit level and the response to TRH may be useful indicators for assessing the operative outcome, especially in nonfunctioning adenoma patients who have no other definite endocrine markers.     

Patterns of gastrin secretion in patients with nonfunctioning pituitary adenomas.

The presence of gastrin in pituitary tissue as well as gastrin hypersecretion by some pituitary adenomas have been documented using different methodological approaches. In the present study, serum gastrin levels were measured in 93 patients with nonfunctioning pituitary adenoma, i.e. a condition lacking a reliable marker of the disease. Elevated gastrin levels (85-2, 180 ng/l; normal range: 15-80 ng/l) were found in 14/93 patients (15%), the highest values being observed in one patient with MEN I syndrome. In all but MEN I hypergastrinemic patient, a severe gastric hypochlorhydria (Basal Acid Output: 0.04 +/- 0.1 mmol H+/h) unresponsive to pentagastrin (Maximum Acid Output: 0.1 +/- 0.2 mmol H+/h) was seen. Secretin injection caused gastrin to increase in the patient with MEN I and in another hypergastrinemic patient. Antiparietal cells autoantibodies were positive in 3/11 patients. No changes in gastrin concentrations were found after administration of several agents usually employed in the evaluation of pituitary function, except a significant gastrin reduction after octreotide injection. In two hypergastrinemic patients who underwent pituitary adenomectomy, the high gastrin levels did not change after surgery. Finally, gastrin was undetectable in the culture media of 15 pituitary adenomas surgically removed from both normo- and hypergastrinemic patients and immunocytological studies of tumor cells did not show any gastrin staining. In conclusion, although in patients with pituitary adenomas serum gastrin evaluation is indicated in order to document the presence of a MEN I syndrome, the present data show that high gastrin levels cannot be taken as a specific marker of nonfunctioning pituitary adenomas unless the peripheral origin of hypergastrinemia is excluded.     

Reversible hypopituitarism in patients with large nonfunctioning pituitary adenomas

Detailed pituitary function studies were conducted on 26 patients with large nonfunctioning pituitary adenomas before and 2-3 months after transsphenoidal adenomectomy. Basal serum PRL, GH, TSH, LH, FSH, and ACTH levels were measured, and dynamic studies of their secretion were made. Preoperatively, GH deficiency was found in all 26 patients (100%), hypogonadism in 25 patients (96%), hypothyroidism in 21 patients (81%), and adrenal insufficiency in 16 patients (62%). Serum PRL levels were low (1.5-4 ng/ml) in 5 patients, normal (5-20 ng/ml) in 9 patients, and mildly elevated (21-53 ng/ml) in the remaining 12 patients. After selective adenomectomy, variable improvement in pituitary function occurred in 17 patients, worsening in 1 patient, and persistence of hypopituitarism in 8 patients. After surgery, normal thyroid function was documented in 12 of the 21 patients (57%) who were hypothyroid preoperatively. Similarly, 6 of the 16 patients (38%) with adrenal insufficiency recovered normal adrenal function, and 8 of the 25 patients (32%) with hypogonadism recovered normal gonadal function. GH deficiency persisted in all but 4 patients (15%). Serum PRL levels decreased in all patients, and only 5 had midly elevated levels after surgery. The presence of a normal or mildly elevated serum PRL level before surgery in these patients was of value in predicting possible recovery of pituitary function after surgery; none of the 5 patients with low preoperative serum PRL levels had any improvement in pituitary function after surgery. A rise in serum TSH levels after TRH administration before surgery also was helpful in predicting possible recovery from hypopituitarism. Most patients who had a rise in serum TSH level in response to TRH stimulation preoperatively recovered some pituitary function after adenomectomy. In contrast, no improvement in pituitary function occurred in patients who had blunted responses to TRH preoperatively. Improvement in pituitary function occurred more often in patients with tumors measuring 25 mm or less than in those with larger tumors. In conclusion, significant improvement in pituitary function may occur after surgical adenomectomy for nonsecreting pituitary tumors. A rise in serum TSH levels in response to TRH stimulation preoperatively suggested the presence of viable pituitary tissue in these patients with hypopituitarism. The presence of a normal or mildly elevated serum PRL level before surgery also suggested the presence of functioning pituitary lactotrophs. These observations suggest that compression of the portal circulation is a possible mechanism for hypopituitarism in this setting.(ABSTRACT TRUNCATED AT 400 WORDS)     

Apoplexy in nonfunctioning pituitary adenomas

Pituitary apoplexy is an uncommon event, occurring due to the infarction and/or haemorrhage usually of a previously unknown pituitary adenoma. It can occur in all adenoma subtypes but is more common in nonfunctioning pituitary adenomas. The physiopathology is not completely clear, and precipitating factors, such as major surgeries, anticoagulant use or pituitary dynamic tests, can be found in up to 40% of patients. The clinical presentation is characterized by a rapid onset with a headache as the main symptom, but visual disturbances can also be present as well as meningism and intracranial hypertension. The diagnosis is based on imaging evaluations, mainly using magnetic resonance imaging, which can show various patterns depending on the timeframe following the occurrence of the apoplectic event. Pituitary hormonal deficits are also common, and the evaluation of hormonal levels is mandatory. Pituitary apoplexy can be managed by surgery or conservative treatment, and a multidisciplinary team is essential for the decision-making process. The outcome is usually positive with both surgical and conservative approaches, but surveillance is needed due to the risk of re-bleeding or tumour recurrence.     

Silent somatotroph pituitary adenomas: an update

Silent growth hormone adenomas (SGHA) are a rare entity of non-functioning pituitary neuroendocrine tumors. Diagnosis is invariably made post-operatively of a tumor immunopositive for GH (and Pit-1 in selected cases) but without clinical acromegaly. Mainly young females are affected, and tumors are often uncovered by investigation for headaches or oligoamenorrhea. Integration of clinical, pathological and biochemical data is required for proper diagnosis. Beside normal IGF-1 levels, a third of SGHAs displays elevated GH levels and some will eventually progress to acromegaly. Almost two-thirds will be mixed GH-prolactin tumors and sparsely-granulated monohormonal GH tumors seems the more aggressive subtype. Recurrence and need for radiation is higher than other non-functioning tumors so close follow-up is warranted.     

Glycoprotein hormone alpha-subunit in pituitary adenomas.

Elevated serum glycoprotein hormone alpha-subunit (alpha-subunit) levels are seen in about one of six patients bearing pituitary adenomas. This finding has particular clinical significance in patients with nonfunctioning pituitary adenomas. Moreover, the measurement of alpha-subunit along with the calculation of the molar ratio between alpha-subunit and TSH, LH, or FSH is helpful in the diagnosis of glycoprotein hormone-secreting pituitary adenomas. Since serum alpha-subunit levels may vary greatly in several physiologic and pathologic conditions, care has to be taken to differentiate abnormal from normal states of alpha-subunit hypersecretion as well as to exclude causes of alpha-subunit overproduction only casually associated with the presence of pituitary tumors.     

Postoperative treatment of clinically nonfunctioning pituitary adenomas with dopamine agonists decreases tumour remnant growth

OBJECTIVE: There is no consensus as to the optimal postoperative treatment of patients with clinically nonfunctioning pituitary adenomas (NFPA) in whom total tumour removal has not been achieved. In this study we assessed whether dopamine agonist (DA) treatment can prevent postoperative remnant enlargement in NFPA. DESIGN AND METHODS: Thirty-three patients (25 men/8 women; mean age, 61.7 +/- 11.2 years; mean follow-up, 40.6 +/- 4.8 months) were treated with DA, and their outcome was compared to that of 47 untreated patients (33 men/14 women; mean age, 59 +/- 2 years; mean follow-up, 42.9 +/- 4.2 months). RESULTS: Tumour mass decreased or remained stable in 18/20 patients in whom DA treatment was initiated upon detection of residual tumour on postoperative MRI (group I). In 13 subjects (group II), DA therapy was started when tumour remnant growth became evident during the course of routine follow-up. Tumour growth stabilized or decreased in 8/13 (61.5%) of these patients. In contrast, tumour size remained stable in only 38.3% (18/47) of the untreated subjects (P < 0.0001 for comparisons among the three groups) and increased in the remaining 29 patients. Tumour enlargement free mean survival time was 103.7 +/- 8.8 months (CI 86.3-121) for group I, 43.9 +/- 9.6 months (CI 25.2-62.8) for group II and 36.7 +/- 3.8 (CI 29.2-44.2) for the control group (P = 0.0017). Treatment vs. control hazard ratio for tumour enlargement was 0.135 for group I (P = 0.007, 95% CI 0.032-0.577) and 0.892 for group II (P = 0.817; 95% CI 0.34-2.34). CONCLUSIONS: Dopamine agonist therapy is associated with a decreased prevalence of residual tumour enlargement in patients with nonfunctioning pituitary adenomas, particularly when treatment is instituted before tumour remnant growth is detected.     

Glycoprotein hormone alpha-subunit production in somatotroph adenomas with and without Gs alpha mutations.

Activating mutations of the Gs alpha subunit have been identified in a subset of somatotroph adenomas. The mutant form of the Gs alpha subunit causes persistent activation of adenylyl cyclase and consequently results in high intracellular levels of cAMP. Because cAMP is known to stimulate the synthesis of the glycoprotein hormone (GPH) alpha-subunit as well as GH, we examined somatotroph tumors with and without Gs alpha mutations for GPH alpha-subunit production. GPH alpha-subunit production was assessed in vivo by measuring serum hormone levels and in vitro by analyzing hormone secretion by cultured pituitary tumor cells. DNA was extracted from the pituitary tumors of 26 acromegalic patients. The Gs alpha gene was amplified by the polymerase chain reaction and screened for mutations at codons 201 and 227 using oligonucleotide specific hybridization. Nine of the 26 tumors (35%) had point mutations at Arg 201. Seven of these tumors contained a CGT to TGT mutation (Arg to Cys) and 2 contained a CGT to CAT mutation (Arg to His). No mutations were detected at codon 227. There were no significant differences in age, sex distribution, tumor size, or serum levels of GH or insulin-like growth factor-1 between the groups of patients with or was Gs alpha mutations. The mean serum level of the free GPH alpha-subunit was 1.9-fold higher in the group with Gs alpha mutations (0.48 +/- 0.37 micrograms/L) than in patients without mutations (0.25 +/- 0.17) (P less than 0.05). In pituitary tumor cell culture, 75% of somatotroph tumors with Gs alpha mutations secreted free GPH alpha-subunit into the media compared with 45% of tumors without Gs alpha mutations. The amount of GPH alpha-subunit secretion was 12-fold greater in the group of tumors containing the Gs alpha mutation (P less than 0.05). Immunocytochemical detection of the free GPH alpha-subunit was similar in the two groups of patients with 75% positive for the GPH alpha-subunit in tumors with Gs alpha mutations and 67% positive in tumors without mutations (P = 0.69). We conclude that GPH alpha-subunit production occurs in somatotroph tumors with and without Gs alpha mutations. The increased levels of GPH alpha-subunit secretion in vivo and in vitro suggest that the Gs alpha mutation may increase the amount of preexisting GPH alpha-subunit biosynthesis in the tumors, perhaps via activation of the cAMP pathway.     

Dopamine receptor expression and function in clinically nonfunctioning pituitary tumors: comparison with the effectiveness of cabergoline treatment

The aim of this study was to correlate dopamine receptors and D(2) isoform expression with the cabergoline effect on alpha-subunit secretion in vitro and tumor mass in vivo in clinically nonfunctioning pituitary tumors. Eighteen patients were subjected to neurosurgery, and a tumor sample was used for dopamine receptor and D(2) isoform expression evaluation by RT-PCR and the in vitro functional studies. After neurosurgery, nine of 18 patients with persistent tumor were treated with cabergoline and tumor mass was evaluated before and after 1 yr treatment. D(2) receptor was expressed in 67% of cases. D(2long) was found in 50%, D(2short) in 17%, and both D(2) isoforms in 33% of cases. D(4) receptor was also expressed in 17% of cases. The in vitro inhibition of alpha-subunit concentration was found in 56% of cases and was associated with D(2) expression (chi(2) = 5.6; P < 0.05). After 1 yr of cabergoline treatment, tumor shrinkage was evident in 56% of patients and was associated with D(2) expression (chi(2) = 5.6; P < 0.05). The expression of D(2short) rather than D(2long) isoform is associated with the most favorable response of the tumor to cabergoline treatment. In conclusion, this study demonstrates D(2) receptor expression and function in nearly 70% of cases, suggesting a role of this drug in the treatment schedule of clinically nonfunctioning pituitary tumors.     

The postoperative monitoring of nonfunctioning pituitary adenomas

Clinically nonfunctioning pituitary tumors are common in tertiary endocrine practice. Although it is widely accepted that patients with these adenomas require long-term surveillance after surgery-particularly those with macroadenomas, which grow much more frequently than microadenomas-a consensus on postoperative monitoring and treatment strategies is lacking. The indications for radiotherapy, which has seen a decline in use over the past decade, are not clear, although most experts would agree that residual tumor mass after surgery, as well as tumor expansion into the cavernous sinus, indicate the need to consider postoperative radiotherapy. In patients not treated with radiotherapy after surgical treatment of a nonfunctioning adenoma, MRI of the tumor should be performed annually for the first 6 years and every 2 years thereafter. In addition, silent adrenocorticotropic hormone-secreting tumors can behave more aggressively if they recur, and tumor regrowth can also occasionally be found in patients after classical pituitary apoplexy, which suggests that individuals with these conditions should also be monitored carefully after surgery. However, at which point this scanning routine can be ceased remains the subject of debate, as few data on late recurrence of nonfunctioning pituitary adenomas exist.     

Somatostatin and dopamine receptor regulation of pituitary somatotroph adenomas

Somatostatin and dopamine receptors are expressed in normal and tumoral somatotroph cells. Upon receptor stimulation, somatostatin and the somatostatin receptor ligands octreotide, lanreotide, and pasireotide, and to a lesser extent, dopamine and the dopamine analogs bromocriptine and cabergoline, suppress growth hormone (GH) secretion from a GH-secreting pituitary somatotroph adenoma. Somatostatin and dopamine receptors are G_αi-protein coupled that inhibit adenylate cyclase activity and cAMP production and reduce intracellular calcium concentration and calcium flux oscillations. Although their main action on somatotroph cells is acute inhibition of GH secretion, they also may inhibit GH production and possibly somatotroph proliferation. These receptors have been reported to create complexes that exhibit functions distinct from that of receptor monomers. Somatostatin suppression of GH is mediated mainly by somatostatin receptor subtype 2 and to a lesser extent by SST5. Human somatostatin receptor subtype 5 has also been shown to harbor mutations associated with GH levels, somatotroph tumor behavior, and somatostatin receptor ligand (SRL) responsiveness. Reviewing current knowledge of somatostatin and dopamine receptor expression and signaling in normal and tumoral somatotroph cells offers insights into mechanisms underlying SRL and dopamine agonist effectiveness in patients with acromegaly.     

Treatment and follow-up of clinically nonfunctioning pituitary macroadenomas

CONTEXT: Although the majority of pituitary macroadenomas are clinically nonfunctioning, treatments as well as follow-up strategy for this condition lack evidence from randomized studies. Evidence Acquisition: We evaluated the evidence of treatment and follow-up strategies for clinically nonfunctioning adenomas. PubMed was searched for articles on nonfunctioning adenomas in November 2007, and references of selected articles were assessed for potentially relevant articles. Evidence Synthesis: All evidence for treatment and follow-up for nonfunctioning adenomas is based on observational studies. The most effective treatment is transsphenoidal surgery, indicated in patients with visual field defects. A wait-and-see approach may be considered in nonfunctioning macroadenomas not reaching to the optic chiasm. Some of these tumors ( approximately 10%) will show spontaneous regression, whereas in approximately 50% there will be progression within 5 yr observation. Postoperative radiotherapy should not be applied to all patients after surgery but can be considered in patients with large postoperative remnants of the tumor. During follow-up careful assessment and replacement of pituitary insufficiencies should be performed. Magnetic resonance imaging is advised with intervals of 1-3 yr and evaluation of visual fields when appropriate. Recurrence rates are reported to be 6-46% after transsphenoidal surgery, whereas after postoperative radiotherapy, recurrence rates of 0-36% are reported. Long-term sequelae of nonfunctioning macroadenomas are hypopituitarism, persistent visual field defects, and decreased quality of life. Whether nonfunctioning macroadenomas are associated with an increased mortality is still a matter of debate. CONCLUSION: Clinically nonfunctioning pituitary macroadenomas, although benign in nature, need individualized treatment and lifelong radiological and endocrinological follow-up.     

Management of nonfunctioning pituitary tumors: radiotherapy

External beam radiotherapy (RT) is an essential part of the management of intracranial tumors and has been used in treating pituitary adenomas for more than five decades. It has been demonstrated that conventional RT for postoperative residual or progressive nonfunctioning pituitary adenomas (NFAs) present an excellent long-term local tumor control, although its use has been limited because of the potential late toxicity related to radiation treatments. Recent advances in radiation techniques have led to more accurate treatments, rendering obsolete many commonly held views of the “old” radiotherapy. New techniques include intensity modulated radiotherapy, volumetric-modulated arc therapy, and stereotactic techniques, either stereotactic radiosurgery or fractionated stereotactic radiotherapy. New techniques allow the delivering of higher radiation doses to the target with rapid dose fall-off in the surrounding normal tissues, and potentially limiting the long term toxicity of radiation. In this review, we present a critical analysis of the most recent available literature on the use of radiation in patients with NFAs, focusing particularly on the efficacy and safety of radiation stereotactic techniques.     

Management of nonfunctioning pituitary adenomas (NFAs): observation

Clinically nonfunctioning pituitary adenomas (NFAs) range from those causing significant hypothalamic/pituitary dysfunction and visual field compromise due to their large size to those being completely asymptomatic. In the absence of hypersecretion, hypopituitarism or visual field defects, patients with NFAs may be followed by periodic surveillance using MRI to detect tumor enlargement. In some cases, endocrine tests are also needed during observation to discover new pituitary dysfunction. Enlargement of NFAs without treatment occurs in about 10% of microadenomas and 23% of macroadenomas. Growth of a pituitary incidentaloma, the development of visual field defects or the development of hypopituitarism are potential indications for surgery during follow up.     

Silent corticotroph adenomas have unique recurrence characteristics compared with other nonfunctioning pituitary adenomas

Objective The prevalence of silent corticotroph adenomas (SCAs) is not rare among nonfunctioning pituitary adenomas (NFPAs); however, it is unknown whether the clinical significance of SCAs differs from that of NFPAs without ACTH immunoreactivity (non‐SCAs). Our goal was to compare the clinical characteristics and natural history between patients with SCAs and non‐SCAs. Design/patients We reviewed the medical records of all patients who underwent transsphenoidal surgery for NFPAs from January 1990 to October 2007 at the Seoul National University Hospital. Measurements We analysed whether clinical manifestations at diagnosis, postoperative recurrence rate and recurrence characteristics differed between SCA and non‐SCA patients. Results In total, 28 patients with SCAs and 134 patients with non‐SCAs were analysed. The mean age at the time of diagnosis was 44 years (range, 13–67 years) in the SCA group and 50 years (18–79 years) in the non‐SCA group (P = 0·026), with respective follow‐up periods of 5·2 (range, 1·0–16·0 years) and 4·2 years (0·5–16·1 years) (P = 0·255). Overall recurrence rates of SCAs and non‐SCAs were 25·0% and 26·9% respectively (P = 0·839). More than two recurrences (P = 0·001) and recurrence after more than 5 years (P = 0·040) were associated with SCAs. Multiple recurrences of SCAs were confined to younger patients. Conclusion The overall recurrence rate was similar between SCAs and non‐SCAs. However, young patients with SCAs had a higher frequency of multiple and late recurrences, which showed more aggressive tumour behaviour. Therefore, we suggest that patients with SCAs, especially patients diagnosed at a young age, require careful long‐term monitoring.     

Short-term treatment with cabergoline can lead to tumor shrinkage in patients with nonfunctioning pituitary adenomas

This study was carried out to evaluate the effectiveness of cabergoline in the treatment of nonfunctioning pituitary adenomas (NFPA), in a short-term follow-up period. Nineteen patients (10 men and 9 women) followed at the University Hospital of Brasilia and harboring nonfunctioning pituitary macroadenomas were enrolled in the study. Eleven patients were previously submitted to transsphenoidal surgery, and in 8 patients no previous treatment had been instituted. Their response to the use of cabergoline (2 mg/week) by 6 months was evaluated. Significant tumor shrinkage (above 25 % from baseline tumor volume) was observed in 6 (31.6 %) of the 19 patients, and no adverse effects were observed during treatment. In 9 patients (47.4 %), a reduction in tumor volume of at least 10 % was noted, whereas tumor growth was observed in four patients (increase above 25 % was only observed in one patient). Cabergoline (2 mg/week) can lead to significant tumor shrinkage in NFPA in a considerable number of patients, and this effect can be observed early (6 months after starting medication). Thus, this therapeutic strategy may be a low cost and safe alternative for treatment of NFPA in patients with remnant or recurrent tumor after transsphenoidal surgery or in those not operated by contraindications or refusal to surgical procedure.