Applications of Genetic Testing for Endocrine and Metabolic Disorders

Knowledge of inherited diseases and the ability to rapidly, efficiently and comprehensively perform genetic testing are advancing steadily. However, the ideal approach to translate this ability into clinical applications for endocrine disorders has yet to be determined. This work focuses on aspects of clinically translating knowledge of select heritable endocrine and metabolic conditions. For maturity onset diabetes of the young (MODY), a monogenic disorder with no current consensus guidelines governing testing procedures, this work addresses methods to improve detection by validating the use of next generation sequencing-based techniques to identify MODY cases and to detect copy number variations. For very severe hypertriglyceridemia, a largely polygenic trait, this work explores clinical differences associated with the underlying genotype, assesses treatment of pancreatitis, the most severe acute complication of hypertriglyceridemia, and presents a population-based study of Ontario adults to identify the most important modifiable risk factors associated with expression of hypertriglyceridemia, and to identify any gaps in appropriate care for this population. For heterozygous familial hypercholesterolemia, a condition for which universal genetic screening has been recommended, this work explores the personal impact of this diagnosis on the patient in terms of quality of life, lifestyle and self-care habits. The ultimate goal of this project is to expand the available knowledge on how best to translate the laboratory ability and findings into the clinical realm for these select endocrine and metabolic conditions

High aldosterone, hypertension and adrenal adenoma in a 36-year-old pregnant patient: Is this primary aldosteronism?

A 36-year-old woman presented at 16 weeks’ gestation with severe hypertension. In comparison to the non-pregnant reference normal ranges, potassium was 3.1-3.9 mmol/L, aldosterone 2570-3000 pmol/L (N 250-2885) renin was unsuppressed (24-76.4 ng/L (N1.7–23.9)), with aldosterone to renin ratios in the reference range. An adrenal MRI scan demonstrated a 1.8 × 1.4 cm left adrenal adenoma. Primary aldosteronism was strongly suspected and surgery considered. However, she was managed conservatively with labetalol and modified-release nifedipine with no obstetric complications. Post-partum blood pressures remained elevated with normal aldosterone (539 pmol/L), unsuppressed renin (5.2 ng/L) and normal aldosterone-to-renin ratio (104 (N \u3c 144)). Suspected primary hyperaldosteronism is challenging to investigate and manage in pregnancy. The accepted screening and confirmatory tests are either contraindicated or not validated in pregnancy. Pregnancy has significant effects on the renin-angiotensin-aldosterone pathway leading to physiologic elevations in both aldosterone and renin. While primary hyperaldosteronism has been associated with poor pregnancy outcomes, optimal management in pregnancy is not clearly established

Adrenal Cushing Syndrome Diagnosed during Pregnancy: Successful Medical Management with Metyrapone

Adrenal Cushing syndrome during pregnancy is rare, and there is limited information on the effect and safety of metyrapone treatment both for mother and fetus. We present a 24-year-old woman diagnosed with adrenal Cushing syndrome at the end of the second trimester. We elected treatment with metyrapone titrated to 250 mg 3 times daily, resulting in good clinical response and maternal serum and saliva cortisol levels in the upper half of the normal pregnancy range. A healthy male infant was born at 35 weeks\u27 gestation, with no clinical signs of adrenal insufficiency, this despite a low cortisol of 5 nmol/L on the first day of life. We measured metyrapone in maternal and umbilical cord blood samples, demonstrating fetal venous metyrapone levels similar to maternal venous concentration, and a fetal arterial cord concentration at about 60% of the fetal venous cord concentration. This case demonstrates that salivary cortisol levels may be used to monitor the effect of metyrapone on adrenal Cushing syndrome during pregnancy. We show, for the first time in humans, that metyrapone does cross the placenta and may suppress fetal cortisol production without necessarily causing clinical signs of adrenal insufficiency

Adrenal Cushing Syndrome Diagnosed during Pregnancy: Successful Medical Management with Metyrapone

Adrenal Cushing syndrome during pregnancy is rare, and there is limited information on the effect and safety of metyrapone treatment both for mother and fetus. We present a 24-year-old woman diagnosed with adrenal Cushing syndrome at the end of the second trimester. We elected treatment with metyrapone titrated to 250 mg 3 times daily, resulting in good clinical response and maternal serum and saliva cortisol levels in the upper half of the normal pregnancy range. A healthy male infant was born at 35 weeks\u27 gestation, with no clinical signs of adrenal insufficiency, this despite a low cortisol of 5 nmol/L on the first day of life. We measured metyrapone in maternal and umbilical cord blood samples, demonstrating fetal venous metyrapone levels similar to maternal venous concentration, and a fetal arterial cord concentration at about 60% of the fetal venous cord concentration. This case demonstrates that salivary cortisol levels may be used to monitor the effect of metyrapone on adrenal Cushing syndrome during pregnancy. We show, for the first time in humans, that metyrapone does cross the placenta and may suppress fetal cortisol production without necessarily causing clinical signs of adrenal insufficiency

Adrenal Cushing Syndrome Diagnosed during Pregnancy: Successful Medical Management with Metyrapone

Adrenal Cushing syndrome during pregnancy is rare, and there is limited information on the effect and safety of metyrapone treatment both for mother and fetus. We present a 24-year-old woman diagnosed with adrenal Cushing syndrome at the end of the second trimester. We elected treatment with metyrapone titrated to 250 mg 3 times daily, resulting in good clinical response and maternal serum and saliva cortisol levels in the upper half of the normal pregnancy range. A healthy male infant was born at 35 weeks\u27 gestation, with no clinical signs of adrenal insufficiency, this despite a low cortisol of 5 nmol/L on the first day of life. We measured metyrapone in maternal and umbilical cord blood samples, demonstrating fetal venous metyrapone levels similar to maternal venous concentration, and a fetal arterial cord concentration at about 60% of the fetal venous cord concentration. This case demonstrates that salivary cortisol levels may be used to monitor the effect of metyrapone on adrenal Cushing syndrome during pregnancy. We show, for the first time in humans, that metyrapone does cross the placenta and may suppress fetal cortisol production without necessarily causing clinical signs of adrenal insufficiency

Large-scale deletions of the ABCA1 gene in patients with hypoalphalipoproteinemia

Copy-number variations (CNVs) have been studied in the context of familial hypercholesterolemia but have not yet been evaluated in patients with extreme levels of HDL cholesterol. We evaluated targeted, next-generation sequencing data from patients with very low levels of HDL cholesterol (i.e., hypoalphalipoproteinemia) with the VarSeq-CNV (R) caller algorithm to screen for CNVs that disrupted the ABCA1, LCAT, or APOA1 genes. In four individuals, we found three unique deletions in ABCA1: a heterozygous deletion of exon 4, a heterozygous deletion that spanned exons 8 to 31, and a heterozygous deletion of the entire ABCA1 gene. Breakpoints were identified with Sanger sequencing, and the full-gene deletion was confirmed by using exome sequencing and the Affymetrix CytoScan HD array. Previously, large-scale deletions in candidate HDL genes had not been associated with hypoalphalipoproteinemia; our findings indicate that CNVs in ABCA1 may be a previously unappreciated genetic determinant of low levels of HDL cholesterol. By coupling bioinformatic analyses with next-generation sequencing data, we can successfully assess the spectrum of genetic determinants of many dyslipidemias, including hypoalphalipoproteinemia

Simplifying Detection of Copy-Number Variations in Maturity-Onset Diabetes of the Young

Copy-number variations (CNVs) are large-scale deletions or duplications of DNA that have required specialized detection methods, such as microarray-based genomic hybridization or multiplex ligation probe amplification. However, recent advances in bioinformatics have made it possible to detect CNVs from next-generation DNA sequencing (NGS) data. Maturity-onset diabetes of the young (MODY) 5 is a subtype of autosomal-dominant diabetes that is often caused by heterozygous deletions involving the HNF1B gene on chromosome 17q12. We evaluated the utility of bioinformatic processing of raw NGS data to detect chromosome 17q12 deletions in MODY5 patients. NGS data from 57 patients clinically suspected to have MODY but who were negative for pathogenic mutations using a targeted panel were re-examined using a CNV calling tool (CNV Caller, VarSeq version 1.4.3). Potential CNVs for MODY5 were then confirmed using whole-exome sequencing, cytogenetic analysis and breakpoint analysis when possible. Whole-gene deletions in HNF1B, ranging from 1.46 to 1.85 million basepairs in size, were detected in 3 individuals with features of MODY5. These were confirmed by independent methods to be part of a more extensive 17q12 deletion syndrome. Two additional patients carrying a 17q12 deletion were subsequently diagnosed using this method. Large-scale deletions are the most common cause of MODY5 and can be detected directly from NGS data, without the need for additional methods. La variabilité du nombre de copies (CNV, de l’anglais copy-number variation) est due à des événements de délétion ou de duplication de l’ADN à grande échelle qui ont requis des méthodes spécialisées de détection telles que l’hybridation génomique sur microréseau ou la MLPA (de l’anglais multiplex ligation probe amplification). Toutefois, les avancées récentes en bio-informatique ont permis de détecter la CNV à partir des données du séquençage de nouvelle génération (SNG) de l’ADN. Le diabète de la maturité apparaissant chez le jeune (MODY, de l’anglais maturity-onset diabetes of the young) 5 est un sous-type de diabète à transmission autosomique dominante souvent causé par les délétions hétérozygotes du gène HNF1B sur le chromosome 17q12. Nous avons évalué l’utilité du traitement bio-informatique des données brutes du SNG pour détecter les délétions du chromosome 17q12 chez les patients atteints de MODY5. Les données du SNG de 57 patients chez qui il y avait une suspicion clinique de MODY, mais dont les résultats au dépistage des mutations pathogéniques à l’aide d’un panel de mutations ciblées étaient négatifs, ont été revues à l’aide de l’outil d’algorithme appelant CNV (CNV Caller, VarSeq version 1.4.3). La CNV de MODY5 a alors été confirmée au moyen du séquençage de l’exome entier, l’analyse cytogénétique et l’analyse des points de cassure lorsque c’était possible. Les délétions du gène entier en HNF1B, qui vont de 1,46 à 1,85 million de paires de base en taille, ont été détectées chez 3 individus ayant des caractéristiques de MODY5. Celles-ci ont été confirmées par des méthodes indépendantes comme faisant partie d’un syndrome de délétion plus importante du 17q12. Deux autres patients porteurs d’une délétion 17q12 ont subséquemment reçu un diagnostic à l’aide de cette méthode. Les délétions à grande échelle sont la cause la plus fréquente de MODY5 et peuvent être détectées directement à partir des données du SNG sans avoir recours à d’autres méthodes