Relative contributions of technetium Tc 99m sestamibi scintigraphy, intraoperative gamma probe detection, and the rapid parathyroid hormone assay to the surgical management of hyperparathyroidism

HYPOTHESIS

Technetium Tc 99m sestamibi scintigraphy, intraoperative gamma probe detection, and the rapid parathyroid hormone assay have been used to permit a directed operation in patients with hyperparathyroidism. We hypothesized that the coordinated use of these techniques might be particularly useful in patients who require a second operation for hyperparathyroidism.

DESIGN

Retrospective analysis was performed to determine the specific contribution of these technologies to the surgical management of patients with hyperparathyroidism who underwent evaluation by at least 2 of these techniques between April 1996 and October 1999.

SETTING

Patients were evaluated and treated by an endocrine tumor surgery group within a tertiary care referral center.

PATIENTS

Coordinated application of 99mTc-sestamibi scintigraphy, intraoperative gamma probe detection, and/or the rapid parathyroid hormone assay was performed in 32 patients.

RESULTS

Twenty-eight of 32 patients had primary hyperparathyroidism, 3 had multiple endocrine neoplasia type 1, and 1 had secondary hyperparathyroidism. The surgical procedure was an initial cervical exploration in 19 and a second operative procedure in 13. Parathyroidectomy was successful in all patients. A directed anatomic operation was performed in 24 patients, including 11 patients who underwent second operative procedures and 9 patients who underwent minimally invasive procedures under local anesthesia. A directed operation was facilitated by sestamibi scan in 22 of 24 patients, intraoperative gamma probe detection in 5 of 23 patients, and the rapid parathyroid hormone assay in 15 of 15 patients.

CONCLUSIONS

Coordinated application of 99mTc-sestamibi scintigraphy, intraoperative gamma probe detection, and the rapid parathyroid hormone assay allows for successful directed reoperative parathyroidectomy; a minimally invasive procedure may be performed in selected patients.

Pituitary carcinoma containing gonadotropins: treatment by radical excision and cytotoxic chemotherapy: case report

OBJECTIVE AND IMPORTANCE

Pituitary carcinomas are extremely rare. Cases reported in the medical literature in the 20th century included tumors that produced adrenocorticotropic hormone, prolactin, growth hormone, and/or thyrotropin.

CLINICAL PRESENTATION

Here we present a 22-year-old woman with a pituitary carcinoma that was immunohistochemically positive for luteinizing hormone and follicle-stimulating hormone at both the primary and metastatic sites. The patient exhibited elevated serum levels of alpha-subunit.

INTERVENTION

The patient had experienced failure of previous treatments, including standard surgery and radiotherapy, and presented to us for radical resection of the tumor, with exenteration of the involved cavernous sinus. She was pretreated with cytotoxic chemotherapy and continued to receive this therapy after surgery.

CONCLUSION

This is the only documented case of a gonadotropin-staining pituitary carcinoma for which hormone production was proven in both the primary and metastatic tumors. Many benign "nonsecreting" pituitary adenomas actually produce subclinical amounts of gonadotropins, and malignant nonfunctional pituitary neoplasms may do the same.

Use of long-term intravenous phosphate infusion in the palliative treatment of tumor-induced osteomalacia

Tumor-induced osteomalacia is characterized by paraneoplastic defects in vitamin D metabolism, proximal renal tubular functions, and phosphate transport. The resulting hypophosphatemia can cause generalized pain and muscle weakness, which significantly affect the quality of life of the patients. Palliative treatment with calcium, vitamin D, and phosphate replacement is indicated for patients in whom the causative tumor cannot be completely resected. In this report we describe a case of tumor-induced osteomalacia in whom adequate oral doses of phosphate could not be used because of gastrointestinal side-effects. Long term (3-6 months) iv phosphate infusion delivered by ambulatory infusion pumps in combination with oral calcium and vitamin D was used successfully to decrease pain and increase muscle strength. Careful monitoring of serum calcium, phosphate, and creatinine levels and reliable microinfusion technology have allowed the long term use of iv phosphate infusion without serious morbidity. This patient received repeated (three times) phosphate infusions over 8 yr, resulting in laboratory and symptomatic improvement after each course. However, this patient did suffer two episodes of central venous catheter-related infection. Because of potentially serious complications, such as severe hypocalcemia, calcified right ventricular thrombi, and nephrocalcinosis, long term iv phosphate infusion should be reserved for patients who cannot tolerate adequate doses of oral phosphate and for whom the benefits outweigh the risks.

Increased blood pressure in alpha-calcitonin gene-related peptide/calcitonin gene knockout mice

Nerves that contain calcitonin gene-related peptide (CGRP) are components of the sensory nervous system. Although these afferent nerves have traditionally been thought to sense stimuli in the periphery and transmit the information centrally, they also have an efferent vasodilator function. Acute administration of a CGRP receptor antagonist increases the blood pressure (BP) in several models of hypertension, which indicates that this potent vasodilator plays a counterregulatory role to attenuate the BP increase in these settings. To determine the role of this peptide in the long-term regulation of cardiovascular function, including hypertension, we obtained mice that have a deletion of the alpha-calcitonin gene-related peptide (alpha-CGRP) gene. Although the beta-calcitonin gene-related peptide (beta-CGRP) gene is intact in these mice, alpha-CGRP is by far the predominant species of CGRP produced in dorsal root ganglia (DRG) sensory neurons. Initially, we examined the effect of deletion of the alpha-CGRP on baseline BP and beta-CGRP and substance P mRNA expression. Systolic BP was significantly higher in the knockout mice (n=7) compared with wild-type in both male (160+/-6.1 vs 125+/-4.8 mm Hg) and female (163+/-4.8 vs 135+/-33 mm Hg) mice. Next, groups (n=7) of knockout and wild-type mice had catheters surgically placed in the right carotid artery for mean arterial pressure recording. With the animals fully awake and unrestrained, the knockout mice displayed an elevated mean arterial pressure compared with wild-type in both male (139+/-4.9 vs 118+/-4.9 mm Hg) and female (121+/-3.4 vs 107+/-3.1 mm Hg) mice. Northern blot analysis of DRG RNA samples confirmed the absence of alpha-CGRP mRNA in the knockout mice. Substance P mRNA content in DRG was unchanged between the 2 groups; however, beta-CGRP mRNA levels were reduced 2-fold in the knockout mice. These results indicate for the first time that alpha-CGRP may be involved in the long-term regulation of resting BP and suggest that these mice are particularly sensitive to challenges to BP homeostasis because of the loss of a compensatory vasodilator mechanism.

Calcium-induced activation of a mutant G-protein-coupled receptor causes in vitro transformation of NIH/3T3 cells

The calcium-sensing receptor (CaR) is a G-protein-coupled receptor that is widely expressed, has tissue-specific functions, and regulates cell growth. Activating mutations of this receptor cause autosomal dominant hypocalcemia, a syndrome characterized by hypocalcemia and hypercalciuria. The identification of a family with an activating mutation of the CaR (Thr151Met) in which hypocalcemia cosegregates with several unusual neoplasms led us to examine the transforming effects of this mutant receptor. Transfection of NIH/3T3 cells with the mutant but not the normal receptor supported colony formation in soft agar at subphysiologic calcium concentrations. The mutant CaR causes a calcium-dependent activation of the extracellular signal-regulated protein kinase (ERK) 1/2 and Jun-N-terminal kinase/stress-activated (JNK/ SAPK) pathways, but not P38 MAP kinase. These findings contribute to a growing body of information suggesting that this receptor plays a role in the regulation of cellular proliferation, and that aberrant activation of the mutant receptor in this family may play a role in the unusual neoplastic manifestations.

Screening for MEN1 mutations in patients with atypical endocrine neoplasia

BACKGROUND

Most patients from typical multiple endocrine neoplasia type 1 (MEN1) kindreds harbor mutations in the MEN-1 gene, MEN1. We hypothesized that some patients with atypical endocrine neoplasia would also have mutations in MEN1.

METHODS

DNA sequencing analysis of mutations in the coding region of MEN1 was performed with genomic DNA obtained from peripheral blood lymphocytes in a total of 21 patients who had: typical MEN1 (n = 8), clinical features suggestive of MEN1 but without a family history of endocrinopathy (n = 7), and atypical endocrine neoplasia and a family history of endocrinopathy suggestive of MEN1 (n = 6).

RESULTS

All 8 patients with typical MEN1 had mutations in MEN1. None of the 7 patients with features of MEN1, but without a family history of endocrinopathy, had a MEN1 mutation. In contrast, 4 of 6 patients with atypical endocrine neoplasia that included components of MEN1 and a family history of endocrinopathy had mutations in MEN1, including 2 patients with pheochromocytoma.

CONCLUSIONS

Genomic mutations in MEN1 may frequently be identified in patients with atypical endocrine neoplasia, especially in the setting of a family history of endocrinopathy. Atypical presentations of MEN1 may include pheochromocytoma.

Surgical strategy for the treatment of medullary thyroid carcinoma

OBJECTIVE

To evaluate surgical complications, patterns of lymph node metastases, and calcitonin response to compartment-oriented lymphadenectomy in patients with primary or recurrent medullary thyroid carcinoma (MTC).

SUMMARY BACKGROUND DATA

The majority of patients with invasive MTC have metastasis to regional lymph nodes at the time of diagnosis, as evidenced by the frequent finding of persistently elevated calcitonin levels after thyroidectomy and the high rates of recurrence in the cervical lymph nodes reported in retrospective studies. These data have provided the rationale for surgeons to perform a more extensive lymphadenectomy at the time of initial thyroidectomy and to consider reoperative cervical lymphadenectomy in patients with persistently elevated calcitonin levels after thyroidectomy.

METHODS

Forty patients underwent surgery for MTC from 1991 to 1997 (23 sporadic cases, 17 familial cases). Patients were divided into three groups based on whether they had undergone previous thyroidectomy and on the results of standardized staging studies performed after referral to the authors' institution. Group 1 (11 patients) had received no previous surgery; group 2 (13) underwent thyroidectomy before referral and had an elevated calcitonin level without radiologic evidence of local regional or distant metastases; and group 3 (16) underwent thyroidectomy before referral and had an elevated calcitonin level with radiologic evidence of local-regional recurrence. The central neck compartment was dissected in all patients; preoperative staging and the extent of previous surgery dictated the need for lateral (modified radical) neck dissection. After primary or reoperative surgery, calcitonin levels were assessed.

RESULTS

All patients had major reductions in postoperative calcitonin levels. Seven (29%) of 24 patients in groups 1 and 2 achieved normal calcitonin values compared with only 1 (6%) of 16 in group 3. Postoperative complications included seven cases (17%) of permanent hypoparathyroidism; five (71%) of these occurred in group 3. There were no iatrogenic recurrent laryngeal nerve injuries; one patient required recurrent nerve resection to achieve complete tumor extirpation. At a median follow up of 35 months, local recurrence was documented in 5 (13%) of 40 patients.

CONCLUSIONS

Compartment-oriented lymphadenectomy performed early in the course of MTC is safe and may return calcitonin levels to normal in up to 25% of carefully selected patients. However, reoperation for bulky cervical disease (group 3) rarely results in normal calcitonin levels and is associated with a high incidence of permanent hypoparathyroidism.

Hammerhead ribozyme-mediated inactivation of mutant RET in medullary thyroid carcinoma

Activating mutations of the RET proto-oncogene cause hereditary medullary thyroid carcinoma. To examine whether selective inactivation of mutant RET could prevent transformation, a hammerhead ribozyme was designed to cleave RET mRNA containing a transforming mutation of codon 634 TGC --> TAC (Cys634Tyr). In vitro RNA cleavage assay demonstrated that the ribozyme selectively cleaved RET RNA with a Cys634Tyr but not Cys634Arg or the normal sequence. Expression of ribozyme in NIH/3T3 cells prevented RET-mediated colony formation in soft agar. This inhibition required catalytically active ribozyme and was specific for the TAC mutation. Therefore, ribozymes designed to selectively target mutant RET RNA may provide an effective therapeutic in the treatment of this syndrome.

A codon 891 exon 15 RET proto-oncogene mutation in familial medullary thyroid carcinoma: a detection strategy

A ser891ala RET proto-oncogene mutation has been previously discovered in a single kindred with familial medullary thyroid carcinoma (FMTC). An additional two probands with this mutation and with medullary thyroid carcinoma (MTC) without any other manifestations of MEN 2 have been identified. In one of thse families, two other individuals also had the mutant sequence and FMTC. Analysis of both cases showed cosegregation of the mutation and MTC. To facilitate detection of this mutation, a primer was engineered which creates a Hha I recognition site in the presence of the mutant sequence. As a result, this codon 891 exon 15 mutation can be identified with a restriction enzyme digestion.

The surgical treatment of medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) is a unique disease in solid tumor oncology due to its ability to secrete calcitonin (iCT), a highly sensitive and specific serum marker of persistent or recurrent disease even at a microscopic level. The relatively long duration of survival experienced by most patients with MTC combined with the visible nature of surgical complications, when they occur, has caused most surgeons to take a conservative approach to the operative management and follow-up of patients with MTC. In contrast, the patient, family physician, and endocrinologist watch the iCT slowly rise, indicative of persistent and usually progressive invasive cancer. Amidst this clinical dilemma, we developed a standardized diagnostic and operative strategy to maximize local-regional tumor control and facilitate patient management.

Polypyrimidine tract-binding protein positively regulates inclusion of an alternative 3'-terminal exon

Polypyrimidine tract-binding protein (PTB) is an abundant vertebrate hnRNP protein. PTB binding sites have been found within introns both upstream and downstream of alternative exons in a number of genes that are negatively controlled by the binding of PTB. We have previously reported that PTB binds to a pyrimidine tract within an RNA processing enhancer located adjacent to an alternative 3'-terminal exon within the gene coding for calcitonin and calcitonin gene-related peptide. The enhancer consists of a pyrimidine tract and CAG directly abutting on a 5' splice site sequence to form a pseudoexon. Here we show that the binding of PTB to the enhancer pyrimidine tract is functional in that exon inclusion increases when in vivo levels of PTB increase. This is the first example of positive regulation of exon inclusion by PTB. The binding of PTB was antagonistic to the binding of U2AF to the enhancer-located pyrimidine tract. Altering the enhancer pyrimidine tract to a consensus sequence for the binding of U2AF eliminated enhancement of exon inclusion in vivo and exon polyadenylation in vitro. An additional PTB binding site was identified close to the AAUAAA hexanucleotide sequence of the exon 4 poly(A) site. These observations suggest a dual role for PTB in facilitating recognition of exon 4: binding to the enhancer pyrimidine tract to interrupt productive recognition of the enhancer pseudoexon by splicing factors and interacting with the poly(A) site to positively affect polyadenylation.

Unknown primary cancer presenting as an adrenal mass: frequency and implications for diagnostic evaluation of adrenal incidentalomas

BACKGROUND

Fine-needle aspiration biopsy to identify adrenal metastasis from an occult primary malignancy has been recommended as part of the evaluation of the patient who presents with an incidentally discovered adrenal mass. This recommendation was assessed by examining the frequency of adrenal involvement in patients with suspected unknown primary cancer.

METHODS

Data from 1715 patients referred for evaluation of suspected unknown primary cancer were retrospectively reviewed.

RESULTS

Of 1639 patients found to have cancer, the adrenal gland was identified as a site of involvement at presentation in 95 (5.8%). Involvement was limited to the adrenal gland in 4 patients (0.2%). All 4 patients had large (> or = 6 cm) adrenal tumors, 3 of 4 had bilateral involvement, and all had symptoms that otherwise mandated evaluation for an occult malignancy; none had a true adrenal incidentaloma.

CONCLUSIONS

Although cancer of an unknown primary site occasionally involves the adrenal gland, metastatic cancer presenting as a true adrenal incidentaloma is extremely rare. Therefore, in the absence of a history of prior malignancy or symptoms, physical examination findings, radiographic findings, or laboratory findings suggestive of an occult malignancy, we do not recommend fine-needle aspiration biopsy as part of the diagnostic evaluation of the patient who presents with a unilateral adrenal mass.

Regulation of alternative polyadenylation by U1 snRNPs and SRp20

Although considerable information is currently available about the factors involved in constitutive vertebrate polyadenylation, the factors and mechanisms involved in facilitating communication between polyadenylation and splicing are largely unknown. Even less is known about the regulation of polyadenylation in genes in which 3'-terminal exons are alternatively recognized. Here we demonstrate that an SR protein, SRp20, affects recognition of an alternative 3'-terminal exon via an effect on the efficiency of binding of a polyadenylation factor to an alternative polyadenylation site. The gene under study codes for the peptides calcitonin and calcitonin gene-related peptide. Its pre-mRNA is alternatively processed by the tissue-specific inclusion or exclusion of an embedded 3'-terminal exon, exon 4, via factors binding to an intronic enhancer element that contains both 3' and 5' splice site consensus sequence elements. In cell types that preferentially exclude exon 4, addition of wild-type SRp20 enhances exon 4 inclusion via recognition of the intronic enhancer. In contrast, in cell types that preferentially include exon 4, addition of a mutant form of SRp20 containing the RNA-binding domain but missing the SR domain inhibits exon 4 inclusion. Inhibition is likely at the level of polyadenylation, because the mutant SRp20 inhibits binding of CstF to the exon 4 poly(A) site. This is the first demonstration that an SR protein can influence alternative polyadenylation and suggests that this family of proteins may play a role in recognition of 3'-terminal exons and perhaps in the communication between polyadenylation and splicing.

Mutational analysis of the GDNF/RET-GDNFR alpha signaling complex in a kindred with vesicoureteral reflux

Glial cell line-derived neurotrophic factor (GDNF) mediates signaling across the cell membrane by interaction with the RET-GDNFR alpha receptor complex. We identified a family in which one member had medullary thyroid carcinoma (MTC) and four members had vesicoureteral reflux (VUR). Knowledge that mutations in the RET proto-oncogene cause MTC and studies documenting genitourinary abnormalities in RET or GDNF knockout mice led us to examine the GDNF/RET-GDNFR alpha signaling complex in this family. RET and GDNF were excluded as the causative VUR gene by haplotype and sequence analysis. The GDNFR alpha gene was mapped to chromosome 10q25-26 by radiation hybrid techniques and was eliminated as the causative gene by haplotype analysis and sequencing of cDNA from an obligate carrier. Sequencing identified a 15-nucleotide deletion in GDNFR alpha mRNA, which was found to code for a single exon; analysis of several cell types revealed an identical mRNA form, indicating that this variant is a product of alternative RNA processing. We conclude that GDNFR alpha maps to 10q25-26 and that its RNA transcript is alternatively processed. Mutation abnormalities in the GDNF/RET-GDNFR alpha signaling system do not cause VUR in this family.

Alternative RNA processing--its role in regulating expression of calcitonin/calcitonin gene-related peptide

The calcitonin/calcitonin gene-related peptide (CT/CGRP) gene is one of the earliest studied examples of alternative RNA processing. The regulatory mechanisms controlling this event are poorly understood. We have identified and characterized an intron element residing in intron 4 of the human CT/CGRP gene. This intron element functions to enhance polyadenylation of an embedded alternative 3'-terminal exon within the CT/CGRP gene and is potentially involved in tissue-specific regulation of CT/CGRP RNA processing.

Bone turnover response to changes in calcium intake is altered in girls and adult women in families with histories of osteoporosis

Heredity and environmental factors contribute to the development of osteoporosis. Because calcium is the major mineral in bone and adolescence is a key period in bone acquisition, we hypothesized that bone turnover would be less responsive to alterations in dietary calcium intake in both girls and adult women from families with histories of osteoporosis. To address this issue, we studied calcium kinetics in the maternal grandmother (age range 56-81 years), mother (age range 32-47 years), and granddaughter (age range 8-15 years) in 10 multigenerational families. In five families, the mother and/or grandmother had osteoporosis (bone mineral density > or = 2 SD below the age-specific mean). To examine both active and passive calcium absorption, families consumed low- (279 +/- 64 mg/day) and high- (1580 +/- 385) calcium diets for 10 days prior to administration of oral (46Ca) and intravenous (42Ca) stable isotopes. Using repeated measures analysis of variance, fractional calcium absorption, true calcium absorption, bone calcium deposition, and the balance in bone calcium turnover were all significantly affected by diet (p < 0.01). Females from nonosteoporotic families had decreased bone calcium resorption with little change in bone calcium deposition during the high-calcium study. In contrast, girls and adult women from osteoporotic families had increased both bone calcium deposition and resorption during the high-calcium period, leading to a less positive balance in bone calcium turnover. A significant interaction between bone status and diet was found for bone calcium resorption (p < 0.05) and approached significance for bone calcium deposition (p < 0.07), effects which were independent of generation. We conclude that girls and women from osteoporotic families have a significantly altered bone turnover response to acute changes in calcium intake.

An overview of molecular abnormalities leading to thyroid carcinogenesis: a 1993 perspective

This discussion reviews molecular abnormalities in thyroid carcinoma and points out areas where these molecular defects might be applicable to thyroid carcinogenesis induced by radiation exposure. Both medullary and papillary follicular thyroid carcinoma are discussed. The multiple endocrine neoplasia type 2 gene on chromosome 10 is one of the genes responsible for medullary thyroid carcinoma. Genes thought to be involved in papillary and follicular thyroid carcinoma include the gsp, ret, trk, ras, met, and p53 oncogenes. Research is continuing to: A) find new genes whose regulation and/or expression may be responsible for these disorders; B) determine the mechanisms by which gene mutations can lead to thyroid carcinogenesis, and C) devise methods to prevent or counter the effects of these mutational events.

Unresolved issues in the genesis and management of multiple endocrine neoplasia type 2

It has been slightly less than 3 years since mutations of the RET proto-oncogene were identified in multiple endocrine neoplasia type 2. The period since the initial report has been one of intense activity with a wide spectrum of mutations identified in exons 10, 11, 13, 14, 15 and 16 of this gene. Recent studies have provided experimental evidence for an activating effect of the exon 11 and 16 mutations. Two questions are addressed in this report: the high rate of false positive tests in prospective screening studies and the implications for future interpretation of this test: and the mechanism of transformation in MEN 2.

Multiple endocrine neoplasia type II and familial medullary thyroid carcinoma. Impact of genetic screening on management

The identification of ret protooncogene mutations in MEN-II and Hirschsprung disease has not only improved the clinical management of these genetic conditions but has also provided important information regarding mechanisms of transformation and neural crest development. An indication of how neural-crest cells migrate during embryonic life and the key processes involved in their differentiation now seems within reach. The continued pace of scientific discovery suggests that our understanding of and ability to prevent or treat hereditary and sporadic forms of MTC will continue to improve.