Diagnosis and Treatment > Medication > Multivitamins

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Andrew R Tang Division of Endocrinology, Department of Medicine, University of Calgary, Calgary, Alberta, Canada

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Laura E Hinz Division of Endocrinology, Department of Medicine, University of Calgary, Calgary, Alberta, Canada

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Aneal Khan Department of Medical Genetics and Pediatrics, University of Calgary, Alberta Children’s Hospital Research Institute, Calgary, Alberta, Canada

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Gregory A Kline Division of Endocrinology, Department of Medicine, University of Calgary, Calgary, Alberta, Canada

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Summary

Hereditary hypophosphatemic rickets with hypercalciuria (HHRH) is a rare, autosomal recessive disorder caused by mutations in the SLC34A3 gene that encodes the renal sodium-dependent phosphate cotransporter 2c (NaPi-IIc). It may present as intermittent mild hypercalcemia which may attract initial diagnostic attention but appreciation of concomitant hypophosphatemia is critical for consideration of the necessary diagnostic approach. A 21-year-old woman was assessed by adult endocrinology for low bone mass. She initially presented age two with short stature, nephrocalcinosis and mild intermittent hypercalcemia with hypercalciuria. She had no evidence of medullary sponge kidney or Fanconi syndrome and no bone deformities, pain or fractures. She had recurrent episodes of nephrolithiasis. In childhood, she was treated with hydrochlorothiazide to reduce urinary calcium. Upon review of prior investigations, she had persistent hypophosphatemia with phosphaturia, low PTH and a high-normal calcitriol. A diagnosis of HHRH was suspected and genetic testing confirmed a homozygous c.1483G>A (p.G495R) missense mutation of the SLC34A3 gene. She was started on oral phosphate replacement which normalized her serum phosphate, serum calcium and urine calcium levels over the subsequent 5 years. HHRH is an autosomal recessive condition that causes decreased renal reabsorption of phosphate, leading to hyperphosphaturia, hypophosphatemia and PTH-independent hypercalcemia due to the physiologic increase in calcitriol which also promotes hypercalciuria. Classically, patients present in childhood with bone pain, vitamin D-independent rickets and growth delay. This case of a SLC34A3 mutation illustrates the importance of investigating chronic hypophosphatemia even in the presence of other more common electrolyte abnormalities.

Learning points:

  • Hypophosphatemia is an important diagnostic clue that should not be ignored, even in the face of more common electrolyte disorders.

  • HHRH is a cause of PTH-independent hypophosphatemia that may also show hypercalcemia.

  • HHRH is a cause of hypophosphatemic nephrocalcinosis that should not be treated with calcitriol, unlike other congenital phosphate wasting syndromes.

  • Some congenital phosphate wasting disorders may not present until adolescence or early adulthood.

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Michelle Maher Bariatric Medicine Service, Centre for Diabetes, Endocrinology and Metabolism, Galway University Hospitals, Galway, Ireland

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Mohammed Faraz Rafey Bariatric Medicine Service, Centre for Diabetes, Endocrinology and Metabolism, Galway University Hospitals, Galway, Ireland
HRB Clinical Research Facility, National University of Ireland Galway, Galway, Ireland

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Helena Griffin Bariatric Medicine Service, Centre for Diabetes, Endocrinology and Metabolism, Galway University Hospitals, Galway, Ireland

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Katie Cunningham Bariatric Medicine Service, Centre for Diabetes, Endocrinology and Metabolism, Galway University Hospitals, Galway, Ireland

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Francis M Finucane Bariatric Medicine Service, Centre for Diabetes, Endocrinology and Metabolism, Galway University Hospitals, Galway, Ireland
HRB Clinical Research Facility, National University of Ireland Galway, Galway, Ireland

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Summary

A 45-year-old man with poorly controlled type 2 diabetes (T2DM) (HbA1c 87 mmol/mol) despite 100 units of insulin per day and severe obesity (BMI 40.2 kg/m2) was referred for bariatric intervention. He declined bariatric surgery or GLP1 agonist therapy. Initially, his glycaemic control improved with dietary modification and better adherence to insulin therapy, but he gained weight. We started a low-energy liquid diet, with 2.2 L of semi-skimmed milk (equivalent to 1012 kcal) per day for 8 weeks (along with micronutrient, salt and fibre supplementation) followed by 16 weeks of phased reintroduction of a normal diet. His insulin was stopped within a week of starting this programme, and over 6 months, he lost 20.6 kg and his HbA1c normalised. However, 1 year later, despite further weight loss, his HbA1c deteriorated dramatically, requiring introduction of linagliptin and canagliflozin, with good response. Five years after initial presentation, his BMI remains elevated but improved at 35.5 kg/m2 and his glycaemic control is excellent with a HbA1c of 50 mmol/mol and he is off insulin therapy. Whether semi-skimmed milk is a safe, effective substrate for carefully selected patients with severe obesity complicated by T2DM remains to be determined. Such patients would need frequent monitoring by an experienced multidisciplinary team.

Learning points:

  • Meal replacement programmes are an emerging therapeutic strategy to allow severely obese type 2 diabetes patients to achieve clinically impactful weight loss.

  • Using semi-skimmed milk as a meal replacement substrate might be less costly than commercially available programmes, but is likely to require intensive multidisciplinary bariatric clinical follow-up.

  • For severely obese adults with poor diabetes control who decline bariatric surgery or GLP1 agonist therapy, a milk-based meal replacement programme may be an option.

  • Milk-based meal replacement in patients with insulin requiring type 2 diabetes causes rapid and profound reductions in insulin requirements, so rigorous monitoring of glucose levels by patients and their clinicians is necessary.

  • In carefully selected and adequately monitored patients, the response to oral antidiabetic medications may help to differentiate between absolute and relative insulin deficiency.

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Yang Timothy Du Department of Diabetes and Endocrinology, Flinders Medical Centre, Bedford Park, South Australia, Australia

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Angus Rutter School of Medicine, Flinders University, Bedford Park, South Australia, Australia

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Jui T Ho Department of Diabetes and Endocrinology, Flinders Medical Centre, Bedford Park, South Australia, Australia

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Summary

A 40-year-old man with achondroplasia presented with symptoms of hypogonadism, low libido and gynaecomastia. He was found to have hypergonadotropic hypogonadism, and karyotype and fluorescent in situ hybridisation analysis showed SRY-positive 46, XX disorder of sex development (DSD). He was tested to have the common activating mutation of the FGFR3 gene implicated in achondroplasia, indicating that he had the two rare conditions independently, with an extremely low incidence of 1 in 400 million. This, to the best of our knowledge, is the first report of an individual having these two rare conditions concurrently. This case highlights that individuals with achondroplasia should have normal sexual development, and in those presenting with incomplete sexual maturation or symptoms of hypogonadism should prompt further evaluation. We also propose a plausible link between achondroplasia and 46, XX DSD through the intricate interactions between the SRY, SOX9 and FGFR9 gene pathways.

Learning points:

  • The SOX9 and FGF9 genes, which are upregulated by the SRY gene, are important in both sex determination in the embryo, as well as endochondral bone growth.

  • Patients with achondroplasia should have normal sexual development and function in the absence of other confounding factors.

  • Patients with achondroplasia who present with symptoms and signs of abnormal sexual development and/or hypogonadism should be appropriately investigated for other causes.

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