Diagnosis and Treatment > Investigation > Serum osmolality

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Alicia R Jones Department of Endocrinology and Diabetes, Western Health, St Albans, Victoria, Australia

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Alan McNeil Dorevitch Pathology, Heidelberg, Victoria, Australia

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Christopher Yates Department of Endocrinology and Diabetes, Western Health, St Albans, Victoria, Australia
Department of Medicine, The University of Melbourne (Royal Melbourne Hospital), Parkville, Victoria, Australia

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Bala Krishnamurthy Department of Endocrinology and Diabetes, Western Health, St Albans, Victoria, Australia
Department of Medicine, The University of Melbourne (St. Vincent’s Hospital), Fitzroy, Victoria, Australia

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Peter S Hamblin Department of Endocrinology and Diabetes, Western Health, St Albans, Victoria, Australia
Department of Medicine, The University of Melbourne (Western Campus), St Albans, Victoria, Australia

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Summary

A variety of neoplastic, inflammatory and congenital conditions can cause pituitary stalk thickening. Differentiating between these causes is important as targeted treatment may be offered. Diagnostic work-up consists of a thorough history, examination, biochemical analysis and imaging. We present the case of a 33-year-old male who presented with diabetes insipidus and had pituitary stalk thickening on magnetic resonance imaging. Further investigations revealed an elevated CSF βhCG, which raised the possibility of an intracranial germ cell tumor. However, when repeated on four different assays, the βhCG levels were discordant. On serial imaging, the pituitary stalk thickening reduced slightly, which would be unexpected for a germ cell tumor. This case raises the difficulties interpreting CSF βhCG, as not all immunoassays for βhCG have been validated for use in CSF. The Roche Diagnostics Elecsys and Siemens Centaur assays have been validated for CSF βhCG, and so we advocate using one of these methods. If unavailable or serum/CSF results are ambiguous, serial MRI is appropriate, with pituitary stalk biopsy considered if the stalk measures >6.5 mm or other imaging abnormalities are present.

Learning points:

  • Most adult patients with central diabetes insipidus have imaging abnormalities on a pituitary MRI. The most common abnormalities are loss of the posterior pituitary bright spot and pituitary stalk thickening, both of which are non-specific.

  • Causes of pituitary stalk thickening include neoplastic, inflammatory, infective and congenital lesions.

  • Investigation of pituitary stalk thickening should encompass the many possible causes and include biochemical analyses as well as imaging of the chest, abdomen and pelvis. Further investigations should be guided by the clinical context, but may include testicular ultrasound, CSF analysis and pituitary stalk biopsy.

  • Germ cell tumors involving the pituitary stalk may be suspected on clinical grounds, but in the absence of a tissue diagnosis (biopsy) confirmation may be difficult and relies on biochemical assessment of blood and possibly CSF as well as serial MRI imaging.

  • CSF βhCG levels should be analyzed on an instrument validated for use in CSF or on multiple instruments, and the pitfalls of testing this marker (false negative in some germ cell tumors, false positives in other conditions, lack of internationally agreed reference ranges for diagnosing germ cell tumors) should be considered when interpreting the results.

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Ricardo A Macau Nephrology Department, Hospital Garcia de Orta

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Tiago Nunes da Silva Endocrinology Department, Hospital Garcia de Orta, Almada, Portugal

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Joana Rego Silva Nephrology Department, Hospital Garcia de Orta

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Ana Gonçalves Ferreira Endocrinology Department, Hospital Garcia de Orta, Almada, Portugal

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Pedro Bravo Nephrology Department, Hospital Garcia de Orta

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Summary

Lithium-induced nephrogenic diabetes insipidus (Li-NDI) is a rare and difficult-to-treat condition. A study in mice and two recent papers describe the use of acetazolamide in Li-NDI in 7 patients (a case report and a 6 patient series). We describe the case of a 63-year-old woman with bipolar disorder treated with lithium and no previous history of diabetes insipidus. She was hospitalized due to a bowel obstruction and developed severe dehydration after surgery when she was water deprived. After desmopressin administration and unsuccessful thiazide and amiloride treatment, acetazolamide was administrated to control polyuria and hydroelectrolytic disorders without significant side effects. To our knowledge, this is the third publication on acetazolamide use in Li-NDI patients.

Learning points:

  • Treatment of lithium-induced nephrogenic diabetes insipidus might be challenging.

  • Vasopressin, amiloride and thiazide diuretics have been used in lithium-induced nephrogenic diabetes insipidus treatment.

  • Acetazolamide might be an option to treat lithium-induced nephrogenic diabetes insipidus patients who fail to respond to standard treatment.

  • The use of acetazolamide in lithium-induced nephrogenic diabetes insipidus must be monitored, including its effects on glomerular filtration rate.

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Jennifer Hague Departments of Clinical Genetics, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK

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Ruth Casey Departments of Diabetes and Endocrinology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
Department of Medical Genetics, University of Cambridge and NIHR Cambridge Biomedical Research Centre and Cancer Research UK Cambridge Centre, Cambridge, UK

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Jonathan Bruty Departments of Clinical Genetics, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK

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Tom Legerton Departments of Clinical Genetics, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK

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Stephen Abbs Departments of Clinical Genetics, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK

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Susan Oddy Department of Clinical Biochemistry, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK

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Andrew S Powlson Departments of Diabetes and Endocrinology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK

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Mohamed Majeed Departments of Diabetes and Endocrinology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK

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Mark Gurnell Departments of Diabetes and Endocrinology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK

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Soo-Mi Park Departments of Clinical Genetics, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK

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Helen Simpson Department of Diabetes and Endocrinology, UCLH NHS Foundation Trust, London, UK

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Summary

Activating mutations in AVPR2 are associated with nephrogenic syndrome of inappropriate antidiuresis (NSIAD). NSIAD causes hyponatremia, decreased serum osmolality and clinical symptoms, which may present from birth or in infancy and include hypotonia, irritability, vomiting and/or seizures. Symptoms in later life are often less specific and include malaise, dizziness, confusion, tiredness and headache. NSIAD is a rare X-linked condition, which is associated with a variable phenotype in males, of whom some present in infancy but others do not become symptomatic until adulthood, or occasionally, never. Female carriers may present with episodes of hyponatremia, usually found incidentally. Literature in this field is limited; namely, two clinical reports describing a female proband, both diagnosed in infancy. We describe, for the first time, the case of an adult female proband with NSIAD, who had longstanding associated symptoms of tiredness, headache, temporary memory loss and mood changes as well as hyponatremia and decreased serum osmolality. A water load test demonstrated an inability to dilute urine and gene sequencing confirmed a recurrent activating mutation in AVPR2. The variant was inherited from the proband’s mother who had had longstanding episodes of transient asymptomatic hyponatremia. This is the third report of a female proband with NSIAD and is the first female reported who sought medical treatment for chronic symptoms from adulthood. This case acts as a reminder of the importance of considering NSIAD as a diagnosis in females of all ages with unexplained hyponatremia.

Learning points:

  • Activating mutations in the AVPR2 gene are associated with the rare X-linked condition nephrogenic syndrome of inappropriate antidiuresis.

  • NSIAD is associated with hyponatremia, decreased serum osmolality and inappropriately increased urinary osmolality. Early clinical symptoms in infancy include hypotonia, irritability, vomiting and/or seizures. Symptoms in later life include malaise, dizziness, confusion, tiredness and headache.

  • NSIAD should be considered in female, as well as male, patients who present with unexplained hyponatremia and decreased serum osmolality. Family history may reveal relevant symptoms or biochemical features in other family members. However, family history may not always be informative due to the variable nature of the condition or if the proband has a de novo pathogenic variant.

  • A water load test with measurement of AVP may be informative in distinguishing NSIAD from SIADH. Measurement of co-peptin levels may be considered, in substitution for direct measurement of AVP.

  • Patients with NSIAD should be counseled about appropriate daily fluid volume intake. Potential episodes of fluid overload should be avoided.

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Joseph Cerasuolo Department of Neurology and Department of Internal Medicine, St. Vincent Hospital, Worcester, Massachusetts, USA

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Anthony Izzo Department of Neurology and Department of Internal Medicine, St. Vincent Hospital, Worcester, Massachusetts, USA

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Summary

Acute hyperglycemia has been shown to cause cognitive impairments in animal models. There is growing appreciation of the numerous effects of hyperglycemia on neuronal function as well as blood–brain barrier function. In humans, hypoglycemia is well known to cause cognitive deficits acutely, but hyperglycemia has been less well studied. We present a case of selective neurocognitive deficits in the setting of acute hyperglycemia. A 60-year-old man was admitted to the hospital for an episode of acute hyperglycemia in the setting of newly diagnosed diabetes mellitus precipitated by steroid use. He was managed with insulin therapy and discharged home, and later, presented with complaints of memory impairment. Deficits included impairment in his declarative and working memory, to the point of significant impairment in his overall functioning. The patient had no structural lesions on MRI imaging of the brain or other systemic illnesses to explain his specific deficits. We suggest that his acute hyperglycemia may have caused neurological injury, and may be responsible for our patient’s memory complaints.

Learning points:

  • Acute hyperglycemia has been associated with poor outcomes in several different central nervous system injuries including cerebrovascular accident and hypoxic injury.

  • Hyperglycemia is responsible for accumulation of reactive oxygen species in the brain, resulting in advanced glycosylated end products and a proinflammatory response that may lead to cellular injury.

  • Further research is needed to define the impact of both acute and chronic hyperglycemia on cognitive impairment and memory.

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Swapna Talluri Internal Medicine

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Raghu Charumathi Internal Medicine

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Muhammad Khan Internal Medicine

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Kerri Kissell Endocrinology, Guthrie Robert Packer Hospital, Sayre, Pennsylvania, USA

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Summary

Central pontine myelinolysis (CPM) usually occurs with rapid correction of severe chronic hyponatremia. Despite the pronounced fluctuations in serum osmolality, CPM is rarely seen in diabetics. This is a case report of CPM associated with hyperglycemia. A 45-year-old non-smoking and non-alcoholic African American male with past medical history of type 2 diabetes, hypertension, stage V chronic kidney disease and hypothyroidism presented with a two-week history of intermittent episodes of gait imbalance, slurred speech and inappropriate laughter. Physical examination including complete neurological assessment and fundoscopic examination were unremarkable. Laboratory evaluation was significant for serum sodium: 140 mmol/L, potassium: 3.9 mmol/L, serum glucose: 178 mg/dL and serum osmolality: 317 mosmol/kg. His ambulatory blood sugars fluctuated between 100 and 600 mg/dL in the six weeks prior to presentation, without any significant or rapid changes in his corrected serum sodium or other electrolyte levels. MRI brain demonstrated a symmetric lesion in the central pons with increased signal intensity on T2- and diffusion-weighted images. After neurological consultation and MRI confirmation, the patient was diagnosed with CPM secondary to hyperosmolar hyperglycemia. Eight-week follow-up with neurology was notable for near-complete resolution of symptoms. This case report highlights the importance of adequate blood glucose control in diabetics. Physicians should be aware of complications like CPM, which can present atypically in diabetics and is only diagnosed in the presence of a high index of clinical suspicion.

Learning points:

  • Despite the pronounced fluctuations in serum osmolality, central pontine myelinolysis (CPM) is rarely seen in diabetics. This case report of CPM associated with hyperglycemia highlights the importance of adequate blood glucose control in diabetics.

  • Physicians should be aware of complications like CPM in diabetics.

  • CPM can present atypically in diabetics and is only diagnosed in the presence of a high index of clinical suspicion.

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Carlos Tavares Bello Endocrinology Department, Hospital de Egas Moniz, Lisboa, Portugal

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Francisco Sousa Santos Endocrinology Department, Hospital de Egas Moniz, Lisboa, Portugal

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João Sequeira Duarte Endocrinology Department, Hospital de Egas Moniz, Lisboa, Portugal

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Carlos Vasconcelos Endocrinology Department, Hospital de Egas Moniz, Lisboa, Portugal

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Summary

Central diabetes insipidus (DI) is a rare clinical entity characterized by low circulating levels of antidiuretic hormone (ADH) presenting with polyuria and volume depletion. Pituitary surgery is the most common cause of central DI in adults. Pituitary and hypothalamic disease, particularly invasive neoplasms, rarely cause DI, being idiopathic cases responsible for the majority of non-surgical cases. HIV patients, especially those with poor virulogical control, are prone to the development of CNS neoplasms, particularly lymphomas. These neoplasms usually become manifest with mass effects and seizures. Central DI and hypopituitarism are uncommon initial manifestations of primary CNS lymphomas. The authors describe the case of 29-year-old female, HIV-positive patient whose CNS lymphoma presented with DI.

Learning points:

  • Central diabetes insipidus has multiple causes and central nervous system lymphomas are not often considered in the differential diagnosis due to their low prevalence.

  • Accurate biochemical diagnosis should always be followed by etiological investigation.

  • The HIV population is at risk for many neoplasms, especially CNS lymphomas.

  • New-onset polyuria in an HIV-positive patient in the absence of focal neurological signs should raise the suspicion for a central nervous system process of neoplastic nature.

  • This clinical entity usually constitutes a therapeutical challenge, often requiring a multidisciplinary approach for optimal outcome.

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Takatoshi Anno Department of General Internal Medicine 1, Kawasaki Medical School, Okayama, Japan

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Fumiko Kawasaki Department of General Internal Medicine 1, Kawasaki Medical School, Okayama, Japan

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Maiko Takai Department of General Internal Medicine 1, Kawasaki Medical School, Okayama, Japan

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Ryo Shigemoto Department of General Internal Medicine 1, Kawasaki Medical School, Okayama, Japan

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Yuki Kan Department of General Internal Medicine 1, Kawasaki Medical School, Okayama, Japan

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Hideaki Kaneto Department of Diabetes, Metabolism and Endocrinology, Kawasaki Medical School, Kurashiki, Japan

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Tomoatsu Mune Department of Diabetes, Metabolism and Endocrinology, Kawasaki Medical School, Kurashiki, Japan

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Kohei Kaku Department of General Internal Medicine 1, Kawasaki Medical School, Okayama, Japan

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Niro Okimoto Department of General Internal Medicine 1, Kawasaki Medical School, Okayama, Japan

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Summary

A 76-year-old man had a hypopituitarism including adrenal insufficiency, hypogonadism and hypothyroidism. Based on various findings including the swelling of the pituitary gland, increase of serum IgG4 level and abundant IgG4-positive plasma cell infiltration in immunostaining of the pituitary gland, we diagnosed this subject as IgG4-related hypophysitis. In general, a high-dose glucocorticoid treatment is effective for IgG4-related disease. His clinical symptom, laboratory data and adrenal insufficiency were almost improved without any therapy. The serum IgG4 level was decreased and pituitary size was normalized with hydrocortisone as physiological replacement. This case report provides the possibility that IgG4 level is decreased spontaneously or with physiological dose of glucocorticoid therapy.

Learning points:

  • We performed the pituitary gland biopsy and histochemical examination glucocorticoid therapy in a subject with IgG4-related hypophysitis.

  • This case report provides the possibility that IgG4 level is decreased spontaneously or with a physiological dose of glucocorticoid therapy. We reported the clinical course of IgG4-related hypophysitis without a high-dose glucocorticoid treatment, although there were a few reports about the retrospective examination.

  • Although the patient had still higher IgG4 level compared to normal range, his clinical symptom disappeared and his laboratory data were improved.

  • We should keep in mind the possibility of IgG4-related hypophysitis when we examine one of the uncertain causes of a hypopituitarism including adrenal insufficiency, hypogonadism and hypothyroidism.

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Peter Taylor Department of Diabetes and Endocrinology, University Hospital of Wales, Heath Park, Cardiff, UK
Thyroid Research Group, Division of Infection and Immunity, School of Medicine, Cardiff University, Heath Park, Cardiff, UK

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Sasan Dehbozorgi Department of Neurosurgery, University Hospital of Wales, Heath Park, Cardiff, UK

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Arshiya Tabasum Department of Diabetes and Endocrinology, University Hospital of Wales, Heath Park, Cardiff, UK

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Anna Scholz Department of Diabetes and Endocrinology, University Hospital of Wales, Heath Park, Cardiff, UK

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Harsh Bhatt Department of Neurosurgery, University Hospital of Wales, Heath Park, Cardiff, UK

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Philippa Stewart Department of Neurosurgery, University Hospital of Wales, Heath Park, Cardiff, UK

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Pranav Kumar Department of Diabetes and Endocrinology, University Hospital of Wales, Heath Park, Cardiff, UK

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Mohd S Draman Department of Diabetes and Endocrinology, University Hospital of Wales, Heath Park, Cardiff, UK
Thyroid Research Group, Division of Infection and Immunity, School of Medicine, Cardiff University, Heath Park, Cardiff, UK

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Alastair Watt Department of Diabetes and Endocrinology, North Devon District Hospital, Barnstaple, UK

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Aled Rees Department of Diabetes and Endocrinology, University Hospital of Wales, Heath Park, Cardiff, UK
Institute of Neuroscience and Mental Health Research Institute, School of Medicine, Cardiff University, Cardiff, UK

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Caroline Hayhurst Department of Neurosurgery, University Hospital of Wales, Heath Park, Cardiff, UK

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Stephen Davies Department of Diabetes and Endocrinology, University Hospital of Wales, Heath Park, Cardiff, UK

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Summary

Hyponatraemia is the most commonly encountered electrolyte disturbance in neurological high dependency and intensive care units. Cerebral salt wasting (CSW) is the most elusive and challenging of the causes of hyponatraemia, and it is vital to distinguish it from the more familiar syndrome of inappropriate antidiuretic hormone (SIADH). Managing CSW requires correction of the intravascular volume depletion and hyponatraemia, as well as mitigation of on-going substantial sodium losses. Herein we describe a challenging case of CSW requiring large doses of hypertonic saline and the subsequent substantial benefit with the addition of fludrocortisone.

Learning points:

  • The diagnosis of CSW requires a high index of suspicion. Distinguishing it from SIADH is essential to enable prompt treatment in order to prevent severe hyponatraemia.

  • The hallmarks of substantial CSW are hyponatraemia, reduced volume status and inappropriately high renal sodium loss.

  • Substantial volumes of hypertonic saline may be required for a prolonged period of time to correct volume and sodium deficits.

  • Fludrocortisone has a role in the management of CSW. It likely reduces the doses of hypertonic saline required and can maintain serum sodium levels of hypertonic saline.

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Victoria John Royal Glamorgan Hospital, Llantrisant, UK

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Philip Evans Consultant Diabetes & Endocrinology, Royal Glamorgan Hospital, Llantrisant, UK

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Atul Kalhan Consultant Diabetes & Endocrinology, Royal Glamorgan Hospital, Llantrisant, UK

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Summary

A 65-year-old woman was admitted to the emergency unit with a 48 h history of generalised weakness and confusion. On examination, she had mild slurring of speech although there was no other focal neurological deficit. She had profound hyponatraemia (serum sodium level of 100 mmol/L) on admission with the rest of her metabolic parameters being within normal range. Subsequent investigations confirmed the diagnosis of small-cell lung cancer with paraneoplastic syndrome of inappropriate antidiuresis (SIAD). She was monitored closely in high-dependency unit with an attempt to cautiously correct her hyponatraemia to prevent sequelae associated with rapid correction. The patient developed prolonged psychosis (lasting over 2 weeks) and displayed delayed dyskinetic movements, even after a gradual increase in serum sodium levels close to 130 mmol/L. To our knowledge, delayed neurological recovery from profound hyponatraemia (without long-term neurological sequelae) has previously not been reported. This case should alert a clinician regarding the possibility of prolonged although reversible psychosis and dyskinetic movements in a patient presenting with profound symptomatic hyponatraemia.

Learning points:

  • Patients with profound hyponatraemia may develop altered sensorium, dyskinesia and psychotic behaviour.

  • Full recovery from psychotic symptoms and dyskinesia may be delayed despite cautious correction of serum sodium levels.

  • Careful and close monitoring of such patients can help avoid long-term neurological sequelae.

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Navira Samad Epworth HealthCare, Melbourne, Victoria, Australia

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Ian Fraser Epworth HealthCare, Melbourne, Victoria, Australia

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Summary

Colonoscopy is a useful tool in modern medicine and is increasingly employed for both diagnostic and treatment reasons. However, its effectiveness is highly reliant on the quality of bowel cleansing. Among different bowel-cleansing agents available, PEG (polyethylene glycol) is considered to be the safest cleansing agent, especially in relation to fluid and electrolyte problems. We present here a case of severe symptomatic hyponatremia that developed after the use of PEG for an elective colonoscopy. This case highlights that despite the use of PEG-based preparations, life-threatening fluid and electrolyte disturbances can still occur in patients with risk factors, such as old age, use of thiazide diuretics and SSRIs, chronic kidney disease, heart failure and a history of electrolyte problems. These patients should be closely monitored when undertaking bowel cleansing and should receive prompt care in the event of complications, to avoid permanent neurological sequelae and death. Rapid correction of sodium levels in patients requiring treatment of hyponatremia should be avoided to prevent complications such as osmotic demyelination syndrome.

Learning points:

  • PEG is considered to be the safest bowel-cleansing agents among different options available, but it can still cause significant side effects in susceptible individuals.

  • Those at risk of developing adverse events include elderly individuals, patients with chronic kidney disease, heart failure or previous history of electrolyte problems and those taking thiazide diuretics and SSRIs.

  • All such patients should be closely monitored i.e. have their metabolic profile checked prior to the commencement of bowel cleansing and a low threshold should be kept for the initiation of investigations and treatment in case of development of symptoms.

  • Medications with a potential of causing fluid and electrolytes such as thiazide diuretics and SSRIs should be withheld while patient is undertaking bowel preparation.

  • Hyponatremia in a hospitalized patient can be multifactorial, and the treatment principles are based on duration of onset, presence of symptoms and patients volume status.

  • Overzealous correction of sodium levels during treatment of hyponatremia can result in serious complications such as osmotic demyelination syndrome.

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