Marianne S. Elston

Experience of prophylactic thyroidectomy in multiple endocrine neoplasia type 2A kindreds with RET codon 804 mutations

Objective and design  Genetic screening in multiple endocrine neoplasia type 2 (MEN 2) has led to specific management guidelines based on genotype–phenotype analysis. However, there is controversy regarding the appropriate age for prophylactic thyroidectomy in families with mutations in codon 804 in exon 14 of the RET proto‐oncogene, where medullary thyroid cancer (MTC) may not develop until adulthood. We prospectively studied two MEN 2A families, one with the V804L and the other with the V804M RET mutation, to report our experience of genetic and biochemical screening and prophylactic thyroidectomy. Family 1 is one of the largest MEN 2A families in the literature, where 22 prophylactic thyroidectomies have been performed.

Factitious Graves' Disease Due to Biotin Immunoassay Interference—A Case and Review of the Literature

CONTEXT Biotin (vitamin B7) is an essential co-factor for four carboxylases involved in fatty acid metabolism, leucine degradation, and gluconeogenesis. The recommended daily intake (RDI) of biotin is approximately 30 μg per day. Low-moderate dose biotin is a common component of multivitamin preparations, and high-dose biotin (10 000 times RDI) has been reported to improve clinical outcomes and quality of life in patients with progressive multiple sclerosis. Biotin is also a component of immunoassays, and supplementation may cause interference in both thyroid and non-thyroid immunoassays. OBJECTIVE To assess whether biotin ingestion caused abnormal thyroid function tests (TFTs) in a patient through assay interference. DESIGN We report a patient with biotin-associated abnormal TFTs and a systematic review of the literature. SETTING A tertiary endocrine service in Hamilton, New Zealand. RESULTS The patient had markedly abnormal TFTs that did not match the clinical context. After biotin cessation, TFTs normalized far more rapidly than possible given the half-life of T4, consistent with assay interference by biotin. Multiple other analytes also tested abnormal in the presence of biotin. CONCLUSION Biotin ingested in moderate to high doses can cause immunoassay interference. Depending on the assay format, biotin interference can result in either falsely high or low values. Interference is not limited to thyroid tests and has the potential to affect a wide range of analytes. It is important for clinicians to be aware of this interaction to prevent misdiagnosis and inappropriate treatment.

Phosphaturic mesenchymal tumors show positive staining for somatostatin receptor 2A (SSTR2A).

Tumor-induced osteomalacia (TIO) is a paraneoplastic syndrome associated with tumors that secrete phosphaturic hormones, most notably fibroblast growth factor 23 (FGF23). The majority of tumors associated with this syndrome show stereotypical histological features and are now known as phosphaturic mesenchymal tumors (PMTs). We postulated that immunohistochemistry for somatostatin receptor 2A (SSTR2A) could be used to definitively identify PMTs or other tumors that cause TIO. Immunohistochemistry for FGF23 and SSTR2A was performed on 15 tumors from 14 patients with a definite diagnosis of TIO. All showed positive staining for both markers. While FGF23 staining was quite focal in some tumors, SSTR2A showed diffuse strong expression. In 40 control tumors not known to be associated with the clinical or biochemical features of TIO, FGF23 expression was found in 2 cases (one aneurysmal bone cyst and one osteosarcoma). SSTR2A expression was found in 9 control tumors (4 synovial sarcomas, 2 hemangiomas, 2 aneurysmal bone cysts and one osteosarcoma). Only one tumor (an aneurysmal bone cyst) showed positive staining for both FGF23 and SSTR2A. SSTR2A also commonly stained neoplastic and non-neoplastic endothelial cells. We conclude that neither FGF23 nor SSTR2A expression are specific for the diagnosis of PMT. However both stains are highly sensitive. Because of its diffuse strong expression and widespread availability, immunohistochemistry for SSTR2A is useful to confirm the diagnosis of PMT in an appropriate setting particularly if material is limited. Negative staining can serve as an excellent rule out test for this diagnosis.

Increased SSTR2A and SSTR3 expression in succinate dehydrogenase-deficient pheochromocytomas and paragangliomas.

Many neuroendocrine tumors, including pheochromocytomas (PCs) and paragangliomas (PGLs), express one or more somatostatin receptors (SSTR1-5). A number of studies have reported SSTR expression in PCs and PGLs. However, receptor expression patterns have been conflicting, and until recently, specific monoclonal antibodies were not available against SSTR1-5. The aim of this study was to compare SSTR1-5 expression in succinate dehydrogenase (SDH)-deficient PCs and PGLs (defined as having absent SDHB immunostaining) to those tumors with normal SDHB staining. Immunohistochemistry for SDHB and SSTR1-5 was performed using specific monoclonal antibodies on archived formalin-fixed, paraffin-embedded tissue from patients who had undergone surgery for PC or PGLs. A total of 182 PC/PGLs were included (129 adrenal, 44 extra-adrenal, 9 metastases); 32 tumors were SDH deficient, whereas 150 tumors had positive SDHB staining. SDH-deficient tumors were more likely to demonstrate moderate or strong staining for SSTR2A and SSTR3 when compared with SDH-sufficient tumors (91% versus 49% [P < .0001] and 50% versus 21% [P = .0008], respectively). Immunostaining for the other SSTRs was not different between SDH-deficient and tumors with preserved SDHB staining. SSTR2A and SSTR3 are more likely to be expressed in SDH-deficient PC/PGLs as compared with tumors demonstrating normal SDHB staining pattern. These findings suggest that the role of somatostatin analogue therapy (unlabeled or radiolabeled) should be reexamined in the context of the underlying SDHB immunohistochemistry pattern.

Thyroid cancer in Graves’ disease: is surgery the best treatment for Graves’ disease?

Graves’ disease is a common cause of thyrotoxicosis. Treatment options include anti‐thyroid medications or definitive therapy: thyroidectomy or radioactive iodine (I131). Traditionally, I131 has been the preferred definitive treatment for Graves’ disease in New Zealand. Reports of concomitant thyroid cancer occurring in up to 17% of Graves’ patients suggest surgery, if performed with low morbidity, may be the preferred option. The aim of this study was to determine the rate of thyroid cancer and surgical outcomes in a New Zealand cohort of patients undergoing thyroidectomy for Graves’ disease.

Identification of Wnt family inhibitors: A pituitary tumor directed whole genome approach

Wnt signaling pathways are important regulators of normal embryological development including that of the pituitary gland. Altered Wnt pathway expression is common in many human tumors however until recently the role of these pathways in human pituitary tumorigenesis has received little attention. The advent of microarray analysis has identified several Wnt pathway inhibitors that are frequently perturbed in pituitary tumors. In this review we summarize the role of these inhibitors in other human tumor types and review the current state of knowledge of Wnt inhibitor expression in pituitary tumors.

Clinical and biochemical characteristics of patients with thyroid-stimulating hormone-secreting pituitary adenomas from one New Zealand centre.

Background:  Thyroid‐stimulating hormone (TSH)‐secreting pituitary adenomas (TSHoma) are a rare cause of thyrotoxicosis and need to be distinguished from the syndrome of resistance to thyroid hormone. Patients with TSHoma may also be misdiagnosed as having primary hyperthyroidism and receive inappropriate treatment directed towards the thyroid gland.

Paraganglioma in Pregnancy: A Case Series and Review of the Literature

CONTEXT Pregnancies complicated by a pheochromocytoma or paraganglioma are very rare, being estimated to occur in 0.007% of all pregnancies. Both the well-being of the mother and fetus need to be considered, and management can be challenging. The optimal management of women with a pheochromocytoma or paraganglioma in pregnancy is not well established. OBJECTIVE The objective of the study was to assess whether there is a difference in fetal or maternal mortality between pheochromocytomas and paragangliomas in pregnancy. DESIGN We present an experience of eight pregnancies in four SDHB germline mutation-positive women with sympathetic paragangliomas, followed by a systematic review of the literature to compare the outcome of paragangliomas with that of pheochromocytomas occurring in pregnancy. RESULTS In our case series, favorable fetal and maternal outcomes were seen in all eight pregnancies. From the systematic review, maternal and fetal mortality were lower in women with paragangliomas, at 3.6% and 12% respectively, compared with 9.8% and 16% in women with pheochromocytomas. CONCLUSION Pregnant women with paragangliomas may be at a lower risk of adverse outcome than those with pheochromocytomas, but both maternal and fetal mortality rates are still higher than that of the general obstetric population.

Early Onset Primary Hyperparathyroidism Associated with a Novel Germline Mutation in CDKN1B

Individuals presenting with primary hyperparathyroidism (PHPT) at a young age commonly have an underlying germline gene mutation in one of the following genes: MEN1, CASR, or CDC73. A small number of families with primary hyperparathyroidism have been identified with germline mutations in CDKN1B and those patients with primary hyperparathyroidism have almost exclusively been women who present in middle age suggesting that the age of onset of PHPT in MEN4 may be later than that of MEN1. We present a case of apparently sporadic PHPT presenting in adolescence with single gland disease associated with a novel CDKN1B germline mutation (heterozygote for a missense mutation in exon 1 of the CDKN1B gene (c.378G>C) (p.E126D)). The implication from this case is that CDKN1B germline mutations may be associated with PHPT at an earlier age than previously thought.

Retrospective Investigation of Testosterone Undecanoate Depot for the Long-term Treatment of Male Hypogonadism in Clinical Practice

INTRODUCTION Testosterone undecanoate depot (TUD) administered intramuscularly is an effective form of testosterone replacement therapy (TRT) for male hypogonadism. Because of the ease of administration, TUD therapy may be preferable to subcutaneously implanted extended release T pellet implants (TI). AIM The primary objective was to retrospectively assess the efficacy and safety of long-term (≥ 2 years therapy) TUD therapy in the clinical setting. The secondary objective was to retrospectively compare TUD with TI therapy. METHODS Retrospective data were collected from the Waikato Hospital Endocrine Database for 179 hypogonadal men treated with TUD for ≥ 2 years from 1998-2011, with 124 of these men receiving previous TI therapy. MAIN OUTCOME MEASURES The main outcome measure for efficacy was serum trough total testosterone (TT), and for safety an increase in hemoglobin (Hb) and/or hematocrit (Hct), rise in prostate-specific antigen (PSA) and/or prostatic biopsy and alteration in body mass index and lipid profile. Additional outcome measures were changes in the dosing and/or interval regimens for TUD therapy. RESULTS Overall, 72% of trough TT levels were in the normal range for TUD therapy compared with 53% of trough TT levels during TI therapy. TUD therapy was well tolerated with 162 men (90.5%) completing 2 years of treatment, and only seven men (3.9%) stopping TUD because of adverse effects. A rise in Hb and/or Hct occurred in 25 men (14%), and a significant rise in PSA in 20 men (13%) at some stage during TUD therapy. At 2 years, 91% of men received the standard 1,000 mg TUD dose with 66% at the standard dosing interval of 10-14 weekly. CONCLUSIONS TUD is an efficacious, safe, and well tolerated form of TRT, and individual optimisation of the dose and/or interval is only required in the minority of men. Particularly given the ease of administration, TUD was the preferred TRT for both patients and clinicians.