The clinical, pathological, and genetic features of familial isolated pituitary adenomas

Pituitary adenomas occur in a familial setting in multiple endocrine neoplasia type 1 (MEN1) and Carney's complex (CNC), which occur due to mutations in the genes MEN1 and PRKAR1A respectively. Isolated familial somatotropinoma (IFS) is also a well-described clinical syndrome related only to patients with acrogigantism. Pituitary adenomas of all types--not limited to IFS--can occur in a familial setting in the absence of MEN1 and CNC; this phenotype is termed familial isolated pituitary adenomas (FIPA). Over the past 7 years, we have described over 90 FIPA kindreds. In FIPA, both homogeneous and heterogeneous pituitary adenoma phenotypes can occur within families; virtually all FIPA kindreds contain at least one prolactinoma or somatotropinoma. FIPA differs from MEN1 in terms of a lower proportion of prolactinomas and more frequent somatotropinomas in the FIPA cohort. Patients with FIPA are significantly younger at diagnosis and have significantly larger pituitary adenomas than matched sporadic pituitary adenoma counterparts. A minority of FIPA families overall (15%) exhibit mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene; AIP mutations are present in only half of IFS kindreds occurring as part of the FIPA cohort. In families with AIP mutations, pituitary adenomas have a penetrance of over 50%. AIP mutations are extremely rare in patients with sporadic pituitary adenomas. This review deals with pituitary adenomas that occur in a familial setting, describes in detail the clinical, pathological, and genetic features of FIPA, and addresses aspects of the clinical approach to FIPA families with and without AIP mutations.     

Familial pituitary adenomas with a heterogeneous functional pattern: clinical and genetic features

Familial pituitary adenoma is a rare syndrome which may present either as isolated lesions, or in association with other endocrine tumors, for example in the frame of multiple endocrine neoplasia (MEN-1) or Carney complex (CNC). The most frequently described forms of familial isolated pituitary adenoma (FIPA) are familial somatotropinomas or prolactinomas. Recently, some cases of familial isolated somatotropinoma have been associated with germline mutations in the aryl hydrocarbon receptor interacting protein (AIP) gene. The present report shows heterogeneous FIPA with 3 subtypes of tumor in 3 individuals of the same family: somatotropinoma in the proband, giant prolactinoma in a brother, and gonadotroph cell macroadenoma in the father. A prospective survey also suggested the occurrence of a silent microadenoma in the proband's sister. Clinical screening was performed in the 3 affected members, the 4th suspected case, and 9 additional, asymptomatic relatives. They had no clinical evidence of associated endocrine lesion suggesting MEN-1 or CNC. Genetic screening for germline mutation of the MEN-1, the gene encoding the protein kinase A (PKA) type 1 alpha regulatory subunit (R1 alpha) (PRKAR1alpha) and AIP gene was negative in 2 affected members. In conclusion, these data suggest that familial pituitary adenomas can occur with a heterogeneous functional pattern that is distinguished from MEN-1 or CNC. The absence of mutation of the recently described AIP gene suggests the implication of other predisposing gene(s). Collaborative, multicentric studies are needed to further define the location of gene(s) involved in heterogeneous FIPA.     

Familial pituitary adenomas

Pituitary adenomas are benign intracranial neoplasms that present a major clinical concern because of hormonal overproduction or compression symptoms of adjacent structures. Most arise in a sporadic setting with a small percentage developing as a part of familial syndromes such as multiple endocrine neoplasia type 1 (MEN1), Carney complex (CNC), and the recently described familial isolated pituitary adenomas (FIPA) and MEN-4. While the genetic alterations responsible for the formation of sporadic adenomas remain largely unknown, considerable advances have been made in defining culprit genes in these familial syndromes. Mutations in MEN1 and PRKAR1A genes are found in the majority of MEN1 and CNC patients, respectively. About 15% of FIPA kindreds present with mutations of the aryl hydrocarbon receptor-interacting protein (AIP) gene. Mutations in the CDKN1B gene, encoding p27(Kip)1 were identified in MEN4 cases. Familial tumours appear to differ from their sporadic counterparts not only in genetic basis but also in clinical characteristics. Evidence suggests that, especially in MEN1 and FIPA, they are more aggressive and affect patients at younger age, therefore justifying the importance of early diagnosis. In this review, we summarize the genetic and clinical characteristics of these familial pituitary adenomas.     

Introduction: Back to basics: mucosal immunity and novel HIV vaccine concepts

The majority of pituitary adenomas occur sporadically, however, about 5% of all cases occur in a familial setting, of which over half are due to multiple endocrine neoplasia type 1 (MEN‐1) and Carney’s complex (CNC). Since the late 1990s we have described non‐MEN1/CNC familial pituitary tumours that include all tumour phenotypes, a condition named familial isolated pituitary adenomas (FIPA). The clinical characteristics of FIPA vary from those of sporadic pituitary adenomas, as patients with FIPA have a younger age at diagnosis and larger tumours. About 15% of FIPA patients have mutations in the aryl hydrocarbon receptor interacting protein gene (AIP), which indicates that FIPA may have a diverse genetic pathophysiology. This review describes the clinical features of familial pituitary adenomas like MEN1, the MEN 1‐like syndrome MEN‐4, CNC, FIPA, the tumour pathologies found in this setting and the genetic/molecular data that have been recently reported.     

Familial isolated pituitary adenomas experience at a single center: clinical importance of AIP mutation screening

We present four FIPA kindred discussing clinical and molecular data and emphasizing the differences regarding AIP status, as well as the importance of genetic screening. Family 1 consists of five patients harboring somatotropinomas with germline E24X mutation in AIP. In one of the patients, acromegaly was diagnosed through active screening, being cured by surgery. Families 2 and 3 are composed of two patients with non-functioning pituitary adenomas. Family 4 comprises patients harboring a prolactinoma and a somatotropinoma. No mutations in AIP were found in these families. No patient in Family 1 was controlled with octreotide treatment, while the acromegalic patient in Family 4 was controlled with octreotide LAR. In conclusion, FIPA is a heterogeneous condition, which may be associated with AIP mutation. Genomic and clinical screening is recommended in families with two or more members harboring pituitary adenomas, allowing early diagnosis and better outcome.     

Pituitary Pathology in Carney Complex Patients

Carney complex (CNC) is a familial multiple neoplasia syndrome with features overlapping those of McCune-Albright syndrome (MAS) and multiple endocrine neoplasia (MEN) type 1 (MEN 1). Like MAS and MEN 1 patients, patients with CNC develop growth hormone (GH)-producing pituitary tumors. Occasionally, these tumors are also prolactin-producing, but there are no isolated prolactinomas or other types of pituitary tumors. In at least some patients with CNC, the pituitary gland is characterized by hyperplastic areas; hyperplasia appears to involve somatomammotrophs only. Hyperplasia most likely precedes the formation of GH-producing adenomas in CNC, as has been suggested in MAS-related somatotropinomas, but has never been seen in MEN 1 patients. In at least one case of a patient with CNC and advanced acromegaly, a GH-producing macroadenoma showed extensive genetic changes at the chromosomal level. So far, half of the patients with CNC have germline inactivating mutations in the PRKAR1A gene; in their pituitary tumors, the normal allele of the PRKAR1A gene is lost. Loss-of-hererozygosity suggests that PRKAR1A, which codes for the regulatory subunit type 1α of the cAMP-dependent protein kinase A (PKA) may act as a tumor-suppressor gene in CNC somatomammotrophs. These data provide evidence for a PRKAR1A-induced somatomammotroph hyperpasia in the pituitary tissue of CNC patients; hyperplasia, in turn may lead to additional genetic changes at the somatic level, which then cause the formation of adenomas in some, but not all, patients.     

The genetic background of acromegaly

Acromegaly is caused by a somatotropinoma in the vast majority of the cases. These are monoclonal tumors that can occur sporadically or rarely in a familial setting. In the last few years, novel familial syndromes have been described and recent studies explored the landscape of somatic mutations in sporadic somatotropinomas. This short review concentrates on the current knowledge of the genetic basis of both familial and sporadic acromegaly.     

Overview of genetic testing in patients with pituitary adenomas

Clinically-relevant pituitary adenomas occur with a prevalence of one case per 1000-1300 of the general population. Although most are sporadic, there are several inherited conditions that incur an increased risk of developing a pituitary adenoma. Multiple endocrine neoplasia type 1 and Carney complex (due to mutations in MEN1 and PRKAR1A, respectively) are established pituitary adenoma predisposition conditions, while multiple endocrine neoplasia type 4 (due to CDKN1B mutations) is an emerging rare condition. Familial isolated pituitary adenomas (FIPA) is a novel condition not associated with these multiple endocrine neoplasias. Mutations in the aryl hydrocarbon receptor interacting protein gene account for about 15% of FIPA kindreds and are associated with about 10-20% of macroadenomas that occur in children, adolescents and young adults. When treating a pituitary adenoma patient, relevant familial and clinical factors such as associated tumors or syndromic features should be assessed at the outset in order to guide the correct choice of genetic testing in appropriate individuals.     

Should aip gene screening be recommended in family members of FIPA patients with R16H variant?

Germline mutations of aryl-hydrocarbon-receptor interacting protein (AIP) are associated with pituitary adenoma predisposition. They occur in 20 % of familial isolated pituitary adenoma (FIPA) and in about 3–5 % of sporadic pituitary adenomas, especially in early onset somatotropinomas and prolactinomas. Our aim was to evaluate the clinical and genetic features of a large Italian FIPA family, where an AIP variant was identified. AIP direct sequencing from genomic DNA was carried out in 16 available family members. AIP R16H carriers also underwent magnetic resonance imaging and hormonal assessments. AIP mutations were also searched in 16 patients with sporadic growth hormone-secreting pituitary adenoma and in 6 unrelated patients in whom pituitary adenoma was excluded. We found an AIP R16H variation in two family members harbouring a pituitary adenoma and in 6 unaffected family members. No AIP mutation was found neither in growth hormone-secreting pituitary adenoma patients, nor in the unrelated patients without pituitary adenoma. We report a FIPA family harbouring an AIP R16H change, supporting the hypothesis that the latter represents a variant of unknown significance.     

Tumor deletion mapping on chromosome 11q13 in eight families with isolated familial somatotropinoma and in 15 sporadic somatotropinomas

CONTEXT: Isolated familial somatotropinoma (IFS) is a rare endocrine disease defined as the occurrence of at least two cases of acromegaly or gigantism in a family that does not exhibit features of Carney complex or multiple endocrine neoplasia type 1. Analysis of the multigenerational expression in families suggests that IFS is inherited as an autosomal dominant disease with incomplete penetrance. The association between the disease and loss of heterozygosity on chromosome 11q13 as well as its linkage to this region has been well established, but the IFS gene still remains unknown. OBJECTIVE: The aim of this report was to narrow the previously described chromosomal region (9.7 cM) to which the gene was previously localized and to evaluate potential candidates. DESIGN AND SETTING: Using haplotyping and allelotyping techniques, we studied eight new families (total of 14 tumors) with IFS and 15 sporadic somatotropinomas. Eighteen polymorphic markers spanning an approximately 9-Mb region on chromosome 11q12.2-11q13.3 were used. MAIN OUTCOME AND RESULTS: Loss of heterozygosity was found in all families and in 40% of sporadic tumors. Although multiple and frequently discontinuous, the presence of allelic loss limited by retentions at their boundaries suggests a new interval of approximately 2.21 Mb on chromosome 11q13.3. Three potential candidate genes (DOC-1R, LOC 399919, and LOC 440049) in this region were sequenced, although no mutations were found. CONCLUSIONS: Identification of the IFS gene is still necessary because it will not only provide insight into the molecular basis of IFS but may also elucidate the pathogenesis of sporadic somatotropinomas.     

Dopaminergic regulation of the hypothalamo-hypophyseal system in patients with hypophyseal adenomas

A study was made of the state of the hypothalamohypophyseal system in patients with different types of chromophobe adenoma. Altogether 62 patients were examined using metoclopramide and Parlodel tests (38 patients were with somatotropinoma, 13--with prolactinoma, 11--with somatotropinoma with hyperprolactinemia). The time course of STH, PRL and TSH secretion in the blood was investigated. Dopaminergic blockade in the Metoclopramide test was shown to cause no change in the time course of PRL secretion in patients with prolactinomas, and a PRL reaction in patients with somatotropinomas and adenomas with PRL and STH hypersecretion was sharply decreased. A paradoxical STH reaction (a decrease) in somatotropinomas and considerable disorders in the type of PRL and TSH secretion in all forms of adenomas was defined in the Parlodel test (a dopaminergic agonist). The results obtained suggest considerable disorders in the dopaminergic regulation of the hypothalamohypophyseal system of patients with chromophobe adenomas and the efficacy of the metoclopramide and Parlodel tests in the differential diagnosis of these conditions.     

Cyclin-dependent kinase inhibitor 1B (CDKN1B) gene variants in AIP mutation-negative familial isolated pituitary adenoma kindreds

Familial isolated pituitary adenoma (FIPA) occurs in families and is unrelated to multiple endocrine neoplasia type 1 and Carney complex. Mutations in AIP account only for 15-25% of FIPA families. CDKN1B mutations cause MEN4 in which affected patients can suffer from pituitary adenomas. With this study, we wanted to assess whether mutations in CDKN1B occur among a large cohort of AIP mutation-negative FIPA kindreds. Eighty-eight AIP mutation-negative FIPA families were studied and 124 affected subjects underwent sequencing of CDKN1B. Functional analysis of putative CDKN1B mutations was performed using in silico and in vitro approaches. Germline CDKN1B analysis revealed two nucleotide changes: c.286A>C (p.K96Q) and c.356T>C (p.I119T). In vitro, the K96Q change decreased p27 affinity for Grb2 but did not segregate with pituitary adenoma in the FIPA kindred. The I119T substitution occurred in a female patient with acromegaly. p27(I119T) shows an abnormal migration pattern by SDS-PAGE. Three variants (p.S56T, p.T142T, and c.605+36C>T) are likely nonpathogenic because In vitro effects were not seen. In conclusion, two patients had germline sequence changes in CDKN1B, which led to functional alterations in the encoded p27 proteins in vitro. Such rare CDKN1B variants may contribute to the development of pituitary adenomas, but their low incidence and lack of clear segregation with affected patients make CDKN1B sequencing unlikely to be of use in routine genetic investigation of FIPA kindreds. However, further characterization of the role of CDKN1B in pituitary tumorigenesis in these and other cases could help clarify the clinicopathological profile of MEN4.     

Isolated Familial Somatotropinoma

The great majority of growth hormone (GH)-secreting pituitary tumors are sporadic, though a few occur with a familial aggregation, either as a component of multiple endocrine neoplasia, type 1 (MEN1) or Carney Complex, or when unassociated with other tumors, as isolated familial somatotropinomas (IFS). This report reviews the clinical and genetic information available from the 46 families reported to date with the latter syndrome. In contrast to sporadic tumors, GH-secreting tumors in IFS occur at an earlier age, especially when all affected family members are from a single generation. The IFS gene is believed to be a tumor suppressor gene, based on the presence of loss of heterozygosity. Although the gene still remains to be identified there is strong evidence for linkage to a locus of less than 10 Mb on chromosome 11q13.1–13.3.     

No evidence of somatic aryl hydrocarbon receptor interacting protein mutations in sporadic endocrine neoplasia

Germline mutations in the aryl hydrocarbon receptor interacting protein (AIP) gene were recently observed in patients with pituitary adenoma predisposition (PAP). Though AIP mutation-positive individuals with prolactin-, mixed growth hormone/prolactin-, and ACTH-producing pituitary adenomas as well as non-secreting pituitary adenomas have been reported, most mutation-positive patients have had growth hormone-producing adenomas diagnosed at relatively young age. Pituitary adenomas are also component tumors of some familial endocrine neoplasia syndromes such as multiple endocrine neoplasia type 1 (MEN1) and Carney complex (CNC). Genes underlying MEN1 and CNC are rarely mutated in sporadic pituitary adenomas, but more often in other lesions contributing to these two syndromes. Thus far, the occurrence of somatic AIP mutations has not been studied in endocrine tumors other than pituitary adenomas. Here, we have analyzed 32 pituitary adenomas and 79 other tumors of the endocrine system for somatic AIP mutations by direct sequencing. No somatic mutations were identified. However, two out of nine patients with prolactin-producing adenoma were shown to harbor a Finnish founder mutation (Q14X) with a complete loss of the wild-type allele in the tumors. These results are in agreement with previous studies in that prolactin-producing adenomas are component tumors in PAP. The data also support the previous finding that somatic AIP mutations are not common in pituitary adenomas and suggest that such mutations are rare in other endocrine tumors as well.     

The parathyroid/pituitary variant of multiple endocrine neoplasia type 1 usually has causes other than p27Kip1 mutations

CONTEXT: One variant of multiple endocrine neoplasia type 1 (MEN1) is defined by sporadic tumors of both the parathyroids and pituitary. The prevalence of identified MEN1 mutations in this variant is lower than in familial MEN1 (7% vs. 90%), suggesting different causes. Recently, one case of this variant had a germline mutation of p27(Kip1)/CDKN1B. OBJECTIVE: The objective was to test p27 in germline DNA from cases with tumors of both the parathyroids and pituitary. DESIGN: Medical record review and sequence analysis in DNA were performed. SETTING: This study involved an inpatient and outpatient referral program for cases of endocrine tumors. PATIENTS: Sixteen index cases had sporadic tumors of two organs, both the parathyroids and the pituitary. There were 18 additional index cases with related features of familial tumors. Five subjects were normal controls. No case had an identified MEN1 mutation. INTERVENTIONS: Clinical status of endocrine tumors was tabulated. Sequencing of germline DNA from index cases and control cases for the p27 gene was performed by PCR. MAIN OUTCOME MEASURES: Endocrine tumor types and their expressions were measured, as were sequence changes in the p27 gene. RESULTS: Tumor features were documented in index cases and families. One p27 germline single nucleotide change was identified. This predicted a silent substitution of Thr142Thr. Furthermore, there was a normal prevalence of heterozygosity for a common p27 polymorphism, making a large p27 deletion unlikely in all or most of these cases. CONCLUSIONS: The MEN1 variant with sporadic parathyroid tumors, sporadic pituitary tumor, and no identified MEN1 mutation is usually not caused by p27 germline mutations. It is usually caused by as yet unknown process(es).     

Multiple endocrine neoplasia type 1 (MEN1) gene mutations in a subset of patients with sporadic and familial primary hyperparathyroidism target the coding sequence but spare the promoter region

Germ line mutations of the multiple endocrine neoplasia type 1 (MEN1) tumour suppressor gene cause MEN1, a rare familial tumour syndrome associated with parathyroid hyperplasia, adenoma and hyperparathyroidism (HP). Here we investigated the role of the MEN1 gene in isolated sporadic and familial HP. Using RT-PCR single-strand conformational polymorphism screening, somatic (but not germ line) mutations of the MEN1 coding sequence were identified in 6 of 31 (19.3%) adenomas from patients with sporadic primary HP, but none in patients (n=16) with secondary HP due to chronic renal failure. MEN1 mutations were accompanied by a loss of heterozygosity (LOH) for the MEN1 locus on chromosome 11q13 in the adenomas as detected by microsatellite analysis. No DNA sequence divergence within the 5' region of the MEN1 gene, containing the putative MEN1 promoter, was detectable in HP adenomas. Clinical characteristics were not different in HP patients with or without MEN1 mutation. Heterozygous MEN1 gene polymorphisms were identified in 9.6% and 25% of patients with primary and secondary HP respectively. In a large kindred with familial isolated familial HP, MEN1 germ line mutation 249 del4 and LOH was associated with the HP phenotype and a predisposition to non-endocrine malignancies. We suggest that the bi-allelic somatic loss of MEN1 wild-type gene expression is involved in the pathogenesis of a clinically yet undefined subset of sporadic primary HP adenomas. MEN1 genotyping may further help define the familial hyperparathyroidism-MEN1 disease complex, but it seems dispensable in sporadic primary HP.     

Pituitary disease in MEN type 1 (MEN1): data from the France-Belgium MEN1 multicenter study

To date, data on pituitary adenomas in MEN type 1 (MEN1) still have to be evaluated. We analyzed the data of a large series of 324 MEN1 patients from a French and Belgian multicenter study. Data on pituitary disease were compared with those from 110 non-MEN1 patients with pituitary adenomas, matched for age, year of diagnosis, and follow-up period. Genetic analysis of the MEN1 gene was performed in 197 of the MEN1 patients. In our MEN1 series, pituitary disease occurred in 136 of 324 (42%), less frequently than hyperparathyroidism (95%, P < 0.001) and endocrine enteropancreatic tumors (54%, P < 0.01). Mean age of onset of pituitary tumors was 38.0+/-15.3 yr (range, 12-83 yr). Pituitary disease was associated with hyperparathyroidism in 90% of cases, with enteropancreatic tumors in 47%, with adrenal tumors in 16%, and with thoracic neuroendocrine tumors in 4%. Pituitary disease was the initial lesion of MEN1 in 17% of all MEN1 patients. MEN1 pituitary adenomas were significantly more frequent in women than in men (50% vs. 31%, P < 0.001). Among the 136 pituitary adenomas, there were 85 prolactinomas and 12 GH-secreting, 6 ACTH-secreting, 13 cosecreting, and 20 nonsecreting tumors. Eighty-five percent of MEN1-related pituitary lesions were macroadenomas (vs. 42% in non-MEN1 patients, P < 0.001), including 32% of invasive cases. Among secreting adenomas, hormonal hypersecretion was normalized, after treatment, in only 42% (vs. 90% in non-MEN1 patients, P < 0.001), with a median follow-up of 11.4 yr. No correlation was found between the type of MEN1 germ-line mutation and the presence or absence of pituitary adenoma. Our study, based on a large group of MEN1 patients, shows that pituitary adenomas occur in 42% of the cases and are characterized by a larger size and a more aggressive presentation than without MEN1.     

Screening for MEN1 tumor suppressor gene mutations in sporadic pituitary tumors

The molecular pathogenesis of the majority of sporadic pituitary tumors is largely unknown. Pituitary adenomas can develop sporadically or as a part of multiple endocrine neoplasia type 1 (MEN1). The MEN1 is thought to be a tumor suppressor gene based on loss of heterozygosity (LOH) for polymorphic markers on 11q13 in tumors of the pancreas, parathyroid, and pituitary. Most patients with familial and sporadic MEN1 carry germ-line mutations in the MEN1 gene. Two previous studies and recently a third one have analyzed mutations by sequencing the MEN1 gene in sporadic pituitary tumors but yielded conflicting results. This study was to investigate and clarify the potential role of MEN1 mutations, in sporadic pituitary adenomas. First, we examined 59 sporadic pituitary adenomas by analyzing LOH on 11q13 in the MEN1 minimal interval with microsatellite analysis. We found 3 tumors with LOH in 1 to 4 polymorphic markers in the MEN1 region. Sequencing analysis did not reveal any mutations in the coding region of the MEN1 gene. However, we found 3 polymorphisms, one of which was a novel CAC to CAT transition encoding His433His, in exon 9. The data show that while LOH occurs in some sporadic pituitary tumors, inactivating mutations of the tumor suppressor gene MEN1 are rare. These results also suggest there may be another additional tumor suppressor gene at this locus which is involved in the pathogenesis of sporadic pituitary neoplasms.     

Validation of immunohistochemistry for somatostatin receptor subtype 2A in human somatotropinomas: comparison between quantitative real time RT-PCR and immunohistochemistry

Somatostatin receptors subtype 2 (SSTR2) expression in somatotropinomas is recognized as a predictor of response to the currently available somatostatin analogs and may be analyzed, mainly, by quantitative RT-PCR or immunohistochemistry (IHC). The former has the advantages of a higher sensitivity and of being quantitative, while the latter, although semi-quantitative, evaluates protein expression and is routinely used in the evaluation of pituitary adenomas. We aimed to evaluate the SSTR2A protein expression in somatotropinomas and to compare it to our previous data regarding mRNA expression, assessed by quantitative real time RTPCR. Thirteen somatotropinomas were analyzed by IHC and the tumors were scored according to percent of immunostained cells: 0 (<25%), 1 (25-50%) and 2 (>50%). SSTR2A immunostaining was present in all but one somatotropinoma, 4 (31%) tumors were classified as score 0, 4 (31%) as score 1, and 5 (38%) as score 2. Median SSTR2 mRNA content was significantly different among the three IHC scores (p=0.036) and was lower in the score 0 than in the score 2 (p=0.016). The finding that there is a positive correlation between RT-PCR and IHC indicates that IHC can be applied in order to assess the SSTR2A content in somatotropinomas.