Expression of Neuropeptide Y and Its Relationship with Molecular and Morphological Changes in Human Pituitary Adenomas.

The purpose of this study was to explore the role of neuropeptide Y (NPY) on molecular and histological changes in human pituitary adenomas. The localization of NPY and its expression at the protein, messenger RNA (mRNA), and receptor levels were investigated here in different subcategories of pituitary adenomas. Immunohistochemical staining was performed in all cases to assess expression of NPY. Reverse transcription-polymerase chain reaction (RT-PCR) was used to study the mRNA expression of NPY. NPY subcellular localization was observed using immunoelectron microscopy in cytoplasm, rough endoplasmic reticulum, and cell matrix in four of the six cases of pituitary adenoma. NPY protein expression was observed in 59.6% of 57 cases of pituitary adenoma and in 2 cases of pituitary hyperplasia. mRNA expression of NPY was observed in all 57 cases of pituitary adenoma and in 2 cases of pituitary hyperplasia. Significantly different levels of expression were observed across different subcategories of pituitary adenoma. mRNA expression of Y1R and Y2R was observed across all subcategories of pituitary adenomas, and a positive correlation was observed between NPY and Y2R. In conclusion, evidence is provided here for the expression of NPY and its receptors, Y1R and Y2R, in human pituitary adenoma, and the levels of expression were found to differ across different subcategories. Differences in expression of Y2R in human pituitary adenomas were found to have remarkable statistical significance.

A sensitive and rapid HPLC-MS/MS method for the quantitative determination of trace amount of bromocriptine in small clinical prolactinoma tissue.

Usually, insufficient intratumoral concentration of therapeutic drugs is one of the reasons for tumor treatment failure. However, little is known about intratumoral distribution of bromocriptine in non-responding prolactinomas because of extremely low drug concentration and small prolactinoma tissue samples. In this study, a sensitive, rapid and high-throughput quantitative bioanalytical method has been established by using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) for the determination of bromocriptine at trace level in human prolactinoma tissue. As little as 20 mg (wet weight) tissue sample was required and total analysis time was 6 min in this method. The assay quantifies over a linear range of 50 fg/mg to 5 pg/mg, and has a 25 fg/mg limit of detection at a signal/noise ratio of 3. This validated method was successfully used to quantitatively determine bromocriptine in clinical post-operative bromocriptine-sensitive and -resistant prolactinomas. The results revealed bromocriptine concentration in resistant prolactinomas (0.49-1.25 pg/mg) was significantly higher than that in sensitive prolactinomas (0.057-0.47 pg/mg). These results provided direct evidence to demonstrate the reseaon for failure of bromocriptine treatment in some patients with prolactinoma was "intrinsic" tumor (cell) resistence, rather than insufficient drug concentration in tumor tissue. Additionaly, this HPLC-MS/MS method has been shown to be suitable for bromocriptine analysis in small amount tissue sample and could be adapted for therapeutic drug monitoring of other clinical medicine.

Role of Ki-67 in acromegalic patients with hyperprolactinemia: retrospective analysis in 61 Chinese Patients.

To evaluate the specific characteristics in acromegalic patients with hyperprolactinemia by analyzing the differences between patients with different Ki-67 values. Between 2002 and 2010, a set of data on 61 patients undergoing transsphenoidal surgery was available at the Department of Neurosurgery, Provincial Hospital Affiliated to Shandong University. Patients were divided into Ki-67 >3% group and <3% group. A retrospective analysis of clinical, hormonal, immunohistochemical, and imaging was observed in all patients. There were no significant differences in age, gender, tumor size and apoplexy between the two groups. Time interval in Ki-67 ≥3% group was longer than <3% group (P=0.037). Patients in Ki-67 >3% group had a higher rate of invasiveness (P=0.048), higher incidences of diabetes mellitus (P=0.036), coarse facial features (P=0.048), large hands and feet (P=0.003), higher GH levels (P<0.05), higher diabetes insipidus rate (P<0.001), and more frequent recurrence (P=0.011) than Ki-67 <3% group. Patients with higher Ki-67 value harbored longer time interval, more aggressive tumors, more acromegaly manifestations, higher GH level, and higher recurrence than patients with lower Ki-67 value.

Giant pituitary adenomas: pathologic-radiographic correlations and lack of role for p53 and MIB-1 labeling.

Giant pituitary adenomas, with diameter ≥4 cm, were formerly considered rare and not surgically approachable. Few United States-based series exist. We reviewed our 10-year experience with these tumors and identified 17 patients, 11 male and 6 female, aged 27 to 65 years. Twelve of 17 cases were either gonadotroph or null cell adenomas and 5 were giant prolactinomas. By neuroimaging, all invaded the cavernous sinus(es) and tumors in 13 patients invaded the skull base. Despite massive size, only 5 showed apoplectic clinical and neuroimaging features. When present, this feature occasionally prompted preoperative consideration of craniopharyngioma. Transsphenoidal surgical excision was possible in all patients, with 3 undergoing planned second-stage reoperations and 2 requiring a second surgery for recurrence (both at 6-year intervals). Despite the aggressive features of massive size and cavernous sinus invasion, mitotic rates and immunohistochemistry (IHC) labeling for p53 and MIB-1, features alleged to be associated with atypical adenomas, were minimally increased. Absence of a role for TP53 and cell cycle markers was further verified on a subset of our cases by microarray and quantitative reverse transcription polymerase chain reaction analyses. Five giant gonadotroph adenomas were compared with 7 nonaggressive, nongiant gonadotroph cell adenomas, and no statistically significant changes in transcript levels of MIB-1 (MKI67) or TP53 were observed. A number of other genes, however, did show differential gene expression. In conclusion, most giant pituitary adenomas are gonadotroph cell adenomas or giant prolactinomas in men. Microarray profiling validates the IHC impression that MIB-1 and p53 IHC do not correlate with aggressive features in the most common type of giant adenoma.

Shotgun proteomic analysis of microdissected postmortem human pituitary using complementary two-dimensional liquid chromatography coupled with tandem mass spectrometer.

The pituitary is responsible for multiple homeostatic functions including metabolism, growth and reproduction. Proteome analysis offers an efficient approach for a comprehensive analysis of pituitary protein expression. The pituitary is usually acquired from postmortem specimens, which may potentially affect the proteome profile by proteolysis. The aim of this study was to determine whether the postmortem pituitary could be used in proteomic analysis combining with Laser capture microdissection (LCM). Digested peptides from LCM captured prolactin (PRL) cells were separated by two dimensional-nanoscale liquid chromatography (2D-nanoLC/MS) and characterized by tandem mass spectrometry (MS). All MS/MS spectrums were searched by SEQUEST and a proteome of 1660 proteins was identified. Category analysis of the proteome revealed an extensive unbiased access to cell component proteins with diverse functional characteristics. The results demonstrated the ability of using 2D-nanoLC/MS to perform sensitive proteomic analysis on limited protein quantities through microdissection. Detailed comparisons between the proteome in question and the one derived from the prolactinoma controls at peptide and protein levels indicated that the two proteomes had similar characters. Overall, our results revealed for the first time the possibility of use of postmortem human pituitary for proteomic research which is important for further studies on disease biomarker identification and molecular mechanisms of prolactinoma tumorigenesis.

Prolactinoma with extensive amyloid deposits: a case report.

Prolactinomas are common benign pituitary neoplasms. Amyloid deposits are rare findings that have been reported in pituitary neoplasms. We report a case of a 48-year old man with a diagnosis of prolactinoma with extensive amyloid deposition. To our knowledge, this is the first case of amyloid in a pituitary neoplasm at our institution.

Molecular pathogenesis of human prolactinomas identified by gene expression profiling, RT-qPCR, and proteomic analyses.

The molecular pathogenesis of prolactinomas has resisted elucidation; with the exception of a RAS mutation in a single aggressive prolactinoma, no mutational changes have been identified. In prolactinomas, a further obstacle has been the paucity of surgical specimens suitable for molecular analysis since prolactionomas are infrequently removed due to the availability and effectiveness of medical therapy. In the absence of mutational events, gene expression changes have been sought and detected. Using high-throughput analysis from a large bank of human pituitary adenomas, we examined these tumors according to their molecular profiles rather than traditional immunohistochemistry. We examined six prolactinomas and eight normal pituitary glands using oligonucleotide GeneChip microarrays, reverse transcription-real time quantitative polymerase chain reaction using 10 prolactinomas, and proteomic analysis to examine protein expression in four prolactinomas. Microarray analyses identified 726 unique genes that were statistically significantly different between prolactinomas and normal glands, whereas proteomic analysis identified four differently up-regulated and 19 down-regulated proteins. Several components of the Notch pathway were altered in prolactinomas, and there was an increased expression of the Pit-1 transcription factor, and the survival factor BAG1 but decreased E-cadherin and N-cadherin expression. Taken together, expression profiling and proteomic analyses have identified molecular features unique to prolactinomas that may contribute to their pathogenesis. In the current era of molecular medicine, these findings greatly enhance our understanding and supercede immunohistochemical diagnosis.

A mutation and expression analysis of the oncogene BRAF in pituitary adenomas.

OBJECTIVE: BRAF is an oncogene that is commonly mutated in both melanomas and papillary thyroid carcinomas, usually at position V600E that leads to constitutive activity in the Ras-mitogen-activated protein kinase (MAPK) pathway. We speculated that this same gene may be either mutated at this site, or overexpressed, in pituitary adenomas. DESIGN AND MEASUREMENTS: We sequenced 37 pituitary adenomas for a mutation at the V600E position. In addition, we investigated B-Raf mRNA expression in normal pituitary (n = 5) and nonfunctioning pituitary adenomas (NFPA) (n = 6) by semiquantitative PCR, and in a further 27 pituitary adenomas of various types and 10 normal pituitaries using real-time quantitative PCR. Finally, we explored B-Raf protein expression in 10 normal pituitaries and 12 NFPAs. RESULTS: No sequence mutations for the substitution V600E were identified. B-Raf mRNA was overexpressed in pituitary adenomas compared to normal pituitary, and this was entirely due to overexpression in NFPAs. NFPAs also showed very variable expression of B-Raf protein, but those tumours showing highest levels of B-Raf mRNA expressed the most B-Raf protein. CONCLUSIONS: Mutations previously seen in the majority of melanomas and a substantial minority of papillary thyroid carcinomas are not a frequent finding in pituitary adenomas. However, overexpression of B-Raf mRNA and protein may be a feature of NFPAs, highlighting overactivity of the Ras-B-Raf-MAP kinase pathway in these tumours.

Do the limits of serum prolactin in disconnection hyperprolactinaemia need re-definition? A study of 226 patients with histologically verified non-functioning pituitary macroadenoma.

BACKGROUND: The differentiation of a pituitary non-functioning macroadenoma from a macroprolactinoma is important for planning appropriate therapy. Serum PRL levels have been suggested as a useful diagnostic indicator. However, values between 2500 and 8000 mU/l are a grey area and are currently associated with diagnostic uncertainty. OBJECTIVE: We wished therefore, to investigate the serum PRL values in a large series of patients presenting with apparently non-functioning pituitary macroadenomas. PATIENTS AND METHODS: All patients presenting to the Department of Endocrinology in Oxford with clinically non-functioning pituitary macroadenomas (later histologically verified) between 1990 and 2005 were studied. Information documented in the notes on the medications and on the presence of conditions capable of affecting the serum PRL levels at the time of blood sampling was also collected. RESULTS: Two hundred and twenty-six patients were identified (median age at diagnosis 55 years, range 18-88 years; 146 males/80 females; 143 gonadotroph, 46 null cell, 25 plurihormonal and 12 silent ACTH adenomas). All tumours had suprasellar extension. At the time of blood sampling 41 subjects were taking medications capable of increasing serum PRL. Hyperprolactinaemia was found in 38.5% (87/226) of the patients. The median serum PRL values in the total group were 386 mU/l (range 16-3257) (males: median 299 mU/l, range 16-1560; females: median 572 mU/l, range 20-3257) and in those not taking drugs capable of increasing serum PRL 363 mU/l (range 16-2565) (males: median 299 mU/l, range 16-1560; females: median 572 mU/l, range 20-2565). Serum PRL < 2000 mU/l was found in 98.7% (223/226) of the total group and in 99.5% (184/185) of those not taking drugs. Among the three subjects with serum PRL > 2000 mU/l, two were taking oestrogen preparations. CONCLUSIONS: Based on a large series of histologically confirmed cases, serum PRL > 2000 mU/l is almost never encountered in nonfunctioning pituitary macroadenomas. Values above this limit in the presence of a macroadenoma should not be surrounded by diagnostic uncertainty (after acromegaly or Cushing's disease have been excluded); a prolactinoma is the most likely diagnosis and a dopamine agonist should be considered as the treatment of choice.

Mapping of somatostatin receptor types in GH or/and PRL producing pituitary adenomas.

BACKGROUND: Somatostatin is a tetradecapeptide exerting inhibitory action on endocrine and exocrine cell secretion and proliferation. Somatostatin receptors (SST) are widely expressed in various neoplasms including endocrine tumours. Using immunohistochemistry, the expression of SST(1), SST(2A), SST(2B), SST(3), SST(4), and SST(5) was studied in tissue microarrays (TMAs), using a series of 90 human pituitary adenomas producing growth hormone and/or prolactin, including 30 of each somatotroph, lactotroph, and mixed somatotroph/lactotroph adenoma type. METHODS: For immunohistochemistry, the standard avidin biotin complex method enhanced by tyramide was used, using polyclonal antisera for all SST types. A four point scoring system was used to assess the membranous immunopositivity. RESULTS: All SST types were positive in all tumour types, showing varying immunoreactivity scores. SST(5) and SST(2A) were the predominant receptors, showing strong expression in high frequency in all three adenoma types. Strong expression of SST(1) was higher in lactotroph adenomas than in other tumour types. CONCLUSIONS: The immunohistochemical results of SST expression are in agreement with most findings of previous molecular studies. The fact that SST(2A) expression is predominant suggests that pharmaceutical octapeptide somatostatin analogues may act through this receptor, while the role of SST(2B) may be merely synergistic.

Pharmacologic resistance in prolactinoma patients.

Pharmacologic resistance to dopamine agonists is defined here as failure to normalize PRL levels and failure to decrease macroprolactinoma size by >or=50%. Failure to normalize PRL levels is found in about one-quarter of patients treated with bromocriptine and 10-15% of those treated with pergolide or cabergoline. Failure to achieve at least a 50% reduction in tumor size occurs in about one-third of those treated with bromocriptine and 10-15% of those treated with pergolide or cabergoline. The cause of dopamine resistance is primarily a decrease in D(2) receptors but the receptors have normal affinity for dopamine. Treatment approaches for patients resistant to dopamine agonists include changing to another dopamine agonist and increasing the dose of the drug as long as there is continued response to the dose increases and no adverse effects with higher doses. Transsphenoidal surgery is also an option. Clomiphene, gonadotropins, and GnRH can be used if fertility is desired. For those not desiring fertility, estrogen replacement may be used unless there is a macroadenoma, in which case control of tumor growth is also an issue and dopamine agonists are generally necessary. In many patients modest or even no reduction in tumor size may be acceptable as long as there is not tumor growth. Hormone replacement (estrogen or testosterone) may cause a decrease in efficacy of the dopamine agonist so that it must be carried out cautiously. Reduction of endogenous estrogen, use of selective estrogen receptor modulators, and aromatase inhibitors are potential experimental approaches.

Mechanism of adrenomedullin-induced prolactin release from human prolactin-releasing adenoma cells.

The mechanism of adrenomedullin-induced prolactin release was investigated in prolactin-secreting human pituitary adenoma cells by intracellular calcium measurement and static incubation study. Adrenomedullin stimulated prolactin release in a concentration-dependent manner. The stimulation was dependent on extracellular sodium and voltage-gated calcium channels. PKA inhibitor attenuated adrenomedullin-induced prolactin release. The mechanism of adrenomedullin action was studied by fura 2-based intracellular calcium measurement. Adrenomedullin increased intracellular calcium concentration in these cells. The increase was dependent on extracellular sodium and voltage-gated calcium channels. PKA inhibitor attenuated the calcium response. These data indicate that adrenomedullin stimulates prolactin release by modulating calcium influx through voltage-gated calcium channels dependently on extracellular sodium. Mechanisms involving sodium-influx mediated depolarization may play a role in the stimulatory action.

Squash smear findings of spherical amyloid in pituitary prolactinoma. A case report.

BACKGROUND: Pituitary prolactinoma containing spherical amyloid is rare. Squash smear findings of spherical amyloid in pituitary prolactinoma are characteristic. CASE: A 25-year-old woman presented with a pituitary tumor. The intraoperative squash smear showed abundant, homogeneous, eosinophilic material with multiple prominent striations. The scattered atypical cells in the periphery contained an irregular, bizarre nucleus; coarse chromatin; occasional prominent nucleoli; rare cytoplasm; and prolactin immunoreactivity. CONCLUSION: The characteristic squash smear findings should be helpful in the diagnosis of this rare tumor.

Reduced expression of the growth hormone and type 1 insulin-like growth factor receptors in human somatotroph tumours and an analysis of possible mutations of the growth hormone receptor.

OBJECTIVE: Clinical acromegaly is characterized by elevated GH secretion in the presence of high circulating IGF-I levels. We hypothesized that the physiological IGF-I/GH negative feedback loop may be reset in somatotroph adenomas, specifically in terms of the level of expression of these receptors or mutations of the GH receptor (GH-R) in such tumours. METHODS: We therefore investigated the full coding sequence of the GH-R in a series of somatotroph and other pituitary adenomas. We also investigated the mRNA expression of these putative feedback receptors in a series of pituitary adenomas and normal pituitary tissue, and their protein expression by immunostaining. Real-time RT-PCR assay was used for the quantification of the type 1 IGF receptor (IGF-R) and GH receptor (GH-R) mRNA, and sequence analysis was performed on the coding region of the GH-R gene. RESULTS: No somatic mutations of the GH-R mRNA were detected in 18 GH-secreting tumours or two nonfunctioning pituitary adenomas (NFPAs). However, the levels of GH-R mRNA were significantly lower in both somatotroph tumours and NFPAs compared to the normal pituitary (P < 0.05 for both). Immunostaining for GH-R also showed significantly less GH-R expression in somatotroph adenomas compared to normal pituitary tissue (P < 0.0001). IGF-R mRNA levels were significantly lower in somatotroph tumours compared to normal pituitary (P = 0.005), and trended lower in corticotroph tumours (P = 0.07), while the other tumour types showed no significant difference from normal pituitary. Immunostaining for IGF-R also showed less IGF-R protein in the somatotroph adenomas compared to the normal pituitary tissue (P < 0.01). CONCLUSIONS: Our findings suggest that decreased feedback inhibition of GH because of somatic mutations of the coding region of the GH-R are unlikely to be a common factor in the pathogenesis of these tumours. Nevertheless, decreased expression of the GH-R and of IGF-R in somatotroph tumours (both at the mRNA and protein level) may, at least in part, help explain the continuous secretion of GH from the tumour despite the high circulating levels of IGF-I and GH.

Clinicopathologic study of 123 cases of prolactin-secreting pituitary adenomas with special reference to multihormone production and clonality of the adenomas.

BACKGROUND: Prolactinoma is the most invasive type of pituitary adenoma and is generally believed to be well-differentiated adenoma and to produce only prolactin (PRL). The factors related to the various biologic behaviors occurring in patients of different ages and sexes await clarification. Since different immunophenotypes of adenoma may show different biologic behaviors and responses to medical agents, the authors examined hormone production and tried to clarify the clonality of plurihormonal prolactinoma. METHODS: Clinicopathologic factors were studied in 123 patients with prolactinomas (40 males and 83 females). The specimens were fixed in either 10% neutral buffered formalin or 70% alcohol and used for light microscopy. Alcohol-fixed tissue was used to extract DNA from 26 samples obtained from female patients for human androgen receptor gene (HUMARA) assay. RESULTS: Sixty one cases (50%) were pure prolactinoma and 62 cases (50%) were plurihormonal prolactinoma. Spearman rank correlation analysis revealed a significant relationship between age and serum PRL level (P = 0.0002), age and tumor volume (P < 0.0001), and tumor volume and serum PRL level (P < 0.0001). Multiple regression analysis showed a significant correlation only between tumor volume and serum PRL level. The Mann-Whitney U test revealed that prolactinomas associated with higher PRL levels, larger adenomas, and higher ages were significantly more invasive to the cavernous sinus and that male patients had significantly higher PRL levels and larger adenomas. The HUMARA assay disclosed that 11 of 13 plurihormonal prolactinomas (85%) were compatible with monoclonal origin. CONCLUSIONS: The current results suggest that not only can various hormones other than PRL be secreted by prolactinoma, but also that most multihormone-producing prolactinomas are monoclonal in origin.

Double pituitary adenomas: a series of three patients.

Multiple pituitary adenomas may occur in up to 1.6-3.3% of patients with Cushing's syndrome. We report three patients with double pituitary adenomas detected at surgery. Two patients had Cushing's disease, but trans-sphenoidal exploration revealed a small prolactinoma in each. One prolactinoma also contained small numbers of basophils. Re-operation in both patients because of persistent Cushing's syndrome showed an ACTH-secreting micro-adenoma. The third patient with acromegaly had two macro-adenomas discovered in different parts of the gland at surgery: one plurihormonal and one null cell tumour. Careful evaluation of pre-operative MRI may not always detect more than one pituitary adenoma.

Immunohistochemical analysis of p27 (Kip1) in human pituitary glands and in various types of pituitary adenomas.

p27 (Kip1) plays regulatory roles in the cell cycle by inhibiting the activity of cyclin dependent kinases (CDKs). This immunohistochemical study is aimed at elucidating the expression of p27 in human pituitary and in various types of pituitary adenomas in order to clarify its role in the regulation of proliferation. Sixteen normal pituitary glands and 179 human pituitary adenomas were used for immunohistochemical studies. The tissues were fixed in 10% formalin and embedded in paraffin. Indirect peroxidase method was performed after heat-induced antigen retrieval using a monoclonal antibody against p27 protein. p27 protein was expressed in the nuclei of all 16 normal human pituitary glands. p27 protein was also expressed in 128 of 179 cases of pituitary adenomas (71.5%). A marked decrease of p27 expression was noted in ACTH-secreting adenomas, 8/20 (40.0%), compared with other types of pituitary adenomas--GH-secreting adenomas, 35/46 (76.1%); PRL-secreting adenomas, 22/33 (66.7%); TSH-secreting adenomas, 8/11 (72.7%); and nonfunctioning adenomas, 55/69 (79.7%). These results suggest that p27 may play some role in the regulation of proliferation in all types of pituitary adenomas. The lower levels of p27 in ACTH-secreting adenoma is of particular interest with respect to the intermediate lobe-derived pituitary tumor developed in p27 knockout mice.

Expression of somatostatin receptors on human pituitary adenomas in vivo and ex vivo.

UNLABELLED: The distribution and biologic activity of somatostatin receptor subtypes (SSTR) in pituitary adenomas is not clarified, especially regarding clinically non-functioning adenomas (NFPA). We therefore characterized SSTR in human pituitary adenomas by combining molecular biology and in vivo scintigraphy. Co-expression of gonadotropin-releasing hormone receptor (GnRH-R) mRNA was also assessed to see whether this feature was associated with adenoma subtype and SSTR status. Pituitary tumor biopsies were obtained during transsphenoidal adenomectomy from 21 patients (11 NFPA, 7 acromegalics, 2 prolactinomas, 1 Cushing's disease). Expression of mRNA encoding the 5 known SSTR subtypes and the GnRH-R was determined by RT-PCR. Twelve patients also underwent a pre-operative somatostatin receptor scintigraphy. Most adenomas (no.=18) expressed mRNA for more than one SSTR. SSTR2 mRNA was expressed in 18 cases, whereas SSTR4 was absent in all but one. SSTR3 was frequently expressed in NFPAs. Somatostatin receptor scintigraphy was positive in most cases, and with a significantly higher uptake index in GH-producing adenomas all of which expressed SSTR2 mRNA. The uptake index appeared to be related to receptor density rather than tumor volume. Expression of GnRH-R mRNA was found in both NFPAs and GH-producing adenomas and was not significantly associated with a particular SSTR subtype population. IN CONCLUSION: 1) the distribution of SSTR is not significantly different between NFPA and GH-producing adenomas; and 2) somatostatin receptor scintigraphy reveals a higher uptake in GH-producing adenomas which is not significantly related to either SSTR distribution or tumor volume.

The release of leptin and its effect on hormone release from human pituitary adenomas.

BACKGROUND: Leptin is the protein product of the obese gene, known to play an important role in body energy balance. The leptin receptor exists in numerous isoforms, the long isoform being the major form involved in signal transduction. Leptin expression has recently been demonstrated in the human pituitary, both in normal tissue and in pituitary adenomas. The long isoform of the leptin receptor has also been shown to be present in pituitary adenomas; however, contrasting results have been obtained regarding its expression in the normal human pituitary. AIM: The aim of this study was (i) to investigate the presence and pattern of distribution of leptin mRNA and the long isoform of its receptor mRNA in the normal pituitary and in different types of pituitary adenomas with RT-PCR; (ii) to study leptin secretion from human pituitary tumours in culture and (iii) to assess in vitro pituitary hormone release following stimulation with human leptin. RESULTS: Leptin receptor long isoform expression was detected in 2/4 GH-secreting adenomas, 12/17 non-functioning adenomas, 5/9 ACTH-secreting adenomas, 1/2 prolactinomas, 2/2 FSH-secreting adenomas and 5/5 normal pituitaries. The receptor long isoform did not segregate with any particular tumour type, and varying levels of expression were detected between the tissues studied. Leptin mRNA was detected at a low level of expression in 2/7 GH-secreting adenomas, 9/14 non-functioning adenomas, 2/3 ACTH-secreting adenomas, 1/3 prolactinomas and 1/3 FSH-secreting adenomas. We were unable to detect leptin mRNA in any of the five normal pituitaries removed at autopsy; however, immunostaining of a non-tumorous pituitary adjacent to an adenoma removed at transsphenoidal surgery showed scattered leptin positive cells. Culture of pituitary adenomas showed that 16/47 released leptin into the incubation media. Leptin release did not correlate with tumour type or with any of the other pituitary hormones released. In vitro leptin stimulation of pituitary tumours caused stimulation of FSH and alpha-subunit secretion from a non-functioning adenoma and TSH secretion from a somatotroph adenoma. CONCLUSION: We conclude that not only is leptin stored within the pituitary, but it may also be released from pituitary cells and modulate other pituitary hormone secretion. Pituitary leptin may therefore be a novel paracrine regulator of pituitary function.

ACTH silent adenoma shrinking under cabergoline.

OBJECTIVES: The authors present a case report that proposes the use of cabergoline treatment in silent ACTH adenoma, an unusual member of the heterogeneous group of the so-called clinically non-functioning pituitary adenomas. DESIGN: Following the clinical and radiological improvement of a recurrent silent ACTH adenoma in a 77-year-old patient treated with cabergoline (0.5 mg every 2 days for 2 years), in vitro studies of the original tumor were performed. METHODS: The original tumor from the patient was studied by in situ hybridization and dopamine D2 receptor autoradiography. It was compared with four macroprolactinomas and two macroadenomas from patients with Cushing's disease. RESULTS: The D2 receptor mRNA signal of the reported case was intense and of the same order of magnitude as that observed in control prolactinomas. Dopamine D2 receptor autoradiography was twice that of control corticotroph adenomas and was close to that observed in prolactinomas. CONCLUSIONS: This is the first description of an in vivo shrinkage of an ACTH silent adenoma under cabergoline. We demonstrate in vitro, the presence of D2 receptors in the primitive tumor in concentrations similar to those found in control prolactinomas. These results suggest that therapeutic trials with cabergoline might be undertaken in recurring cases of ACTH silent tumors and more generally, non-functioning pituitary adenomas.