Diagnosis and Treatment > Investigation > Insulin tolerance
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Department of Internal Medicine, Keiju Medical Center, Nanao, Ishikawa, Japan
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Department of Health Promotion and Medicine of the Future, Kanazawa University, Kanazawa, Ishikawa, Japan
Search for other papers by Takashi Yoneda in
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Search for other papers by Yoshiyu Takeda in
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Summary
Renovascular hypertension (RVHT) is an important and potentially treatable form of resistant hypertension. Hypercortisolemia could also cause hypertension and diabetes mellitus. We experienced a case wherein adrenalectomy markedly improved blood pressure and plasma glucose levels in a patient with RVHT and low-level autonomous cortisol secretion. A 62-year-old Japanese man had been treated for hypertension and diabetes mellitus for 10 years. He was hospitalized because of a disturbance in consciousness. His blood pressure (BP) was 236/118 mmHg, pulse rate was 132 beats/min, and plasma glucose level was 712 mg/dL. Abdominal CT scanning revealed the presence of bilateral adrenal masses and left atrophic kidney. Abdominal magnetic resonance angiography demonstrated marked stenosis of the left main renal artery. The patient was subsequently diagnosed with atherosclerotic RVHT with left renal artery stenosis. His left adrenal lobular mass was over 40 mm and it was clinically suspected the potential for cortisol overproduction. Therefore, laparoscopic left nephrectomy and adrenalectomy were simultaneously performed, resulting in improved BP and glucose levels. Pathological studies revealed the presence of multiple cortisol-producing adrenal nodules and aldosterone-producing cell clusters in the adjacent left adrenal cortex. In the present case, the activated renin-angiotensin-aldosterone system and cortisol overproduction resulted in severe hypertension, which was managed with simultaneous unilateral nephrectomy and adrenalectomy.
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Concomitant activation of the renin-angiotensin-aldosterone system and cortisol overproduction may contribute to the development of severe hypertension and lead to lethal cardiovascular complications.
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Treatment with simultaneous unilateral nephrectomy and adrenalectomy markedly improves BP and blood glucose levels.
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CYP11B2 immunohistochemistry staining revealed the existence of aldosterone-producing cell clusters (APCCs) in the adjacent non-nodular adrenal gland, suggesting that APCCs may contribute to aldosterone overproduction in patients with RVHT.
Research Institute in Biomedical and Health Sciences, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
Search for other papers by Mauro Boronat in
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Summary
Isolated, adult-onset central hypothyroidism is very rare, and its diagnosis can be challenging. A 42-year-old patient was referred for evaluation of a 2.8 cm thyroid nodule. She referred symptoms that could be attributed to hypothyroidism and thyroid tests showed low TSH and normal-low levels of free T4. However, evaluation of the remaining pituitary hormones and pituitary MRI were normal, yet a radionuclide scanning revealed that the thyroid nodule was ‘hot’ and the tracer uptake in the remaining thyroid tissue was suppressed. Interpretation of these studies led to a misdiagnosis of subclinical hyperthyroidism and the patient was treated with radioiodine. Soon after treatment, she developed a frank hypothyroidism without appropriate elevation of TSH and the diagnosis of central hypothyroidism was made a posteriori. Long term follow-up revealed a progressive pituitary failure, with subsequent deficiency of ACTH and GH. This case should alert to the possibility of overlooking central hypothyroidism in patients simultaneously bearing primary thyroid diseases able to cause subclinical hyperthyroidism.
Learning points:
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Although rarely, acquired central hypothyroidism can occur in the absence of other pituitary hormone deficiencies.
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In these cases, diagnosis is challenging, as symptoms are unspecific and usually mild, and laboratory findings are variable, including low, normal or even slightly elevated TSH levels, along with low or low-normal concentrations of free T4.
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In cases with low TSH levels, the coexistence of otherwise common disorders able to cause primary thyroid hyperfunction, such as autonomous nodular disease, may lead to a misdiagnosis of subclinical hyperthyroidism.
Search for other papers by Nikolaos Kyriakakis in
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Search for other papers by Robert D Murray in
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Summary
A male patient presented at the age of 30 with classic clinical features of acromegaly and was found to have elevated growth hormone levels, not suppressing during an oral glucose tolerance test. His acromegaly was originally considered to be of pituitary origin, based on a CT scan, which was interpreted as showing a pituitary macroadenoma. Despite two trans-sphenoidal surgeries, cranial radiotherapy and periods of treatment with bromocriptine and octreotide, his acromegaly remained active clinically and biochemically. A lung mass was discovered incidentally on a chest X-ray performed as part of a routine pre-assessment for spinal surgery 5 years following the initial presentation. This was confirmed to be a bronchial carcinoid tumour, which was strongly positive for growth hormone-releasing hormone (GHRH) and somatostatin receptor type 2 by immunohistochemistry. The re-examination of the pituitary specimens asserted the diagnosis of pituitary GH hyperplasia. Complete resolution of the patient’s acromegaly was achieved following right lower and middle lobectomy. Seventeen years following the successful resection of the bronchial carcinoid tumour the patient remains under annual endocrine follow-up for monitoring of the hypopituitarism he developed after the original interventions to his pituitary gland, while there has been no evidence of active acromegaly or recurrence of the carcinoid tumour. Ectopic acromegaly is extremely rare, accounting for <1% of all cases of acromegaly. Our case highlights the diagnostic challenges differentiating between ectopic acromegaly and acromegaly of pituitary origin and emphasises the importance of avoiding unnecessary pituitary surgery and radiotherapy. The role of laboratory investigations, imaging and histology as diagnostic tools is discussed.
Learning points:
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Ectopic acromegaly is rare, accounting for less than 1% of all cases of acromegaly.
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Ectopic acromegaly is almost always due to extra-pituitary GHRH secretion, mainly from neuroendocrine tumours of pancreatic or bronchial origin.
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Differentiating between acromegaly of pituitary origin and ectopic acromegaly can cause diagnostic challenges due to similarities in clinical presentation and biochemistry.
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Serum GHRH can be a useful diagnostic tool to diagnose ectopic acromegaly.
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Pituitary imaging is crucial to differentiate between a pituitary adenoma and pituitary hyperplasia, which is a common finding in ectopic acromegaly.
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Diagnosing ectopic acromegaly is pivotal to avoid unnecessary interventions to the pituitary and preserve normal pituitary function.
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Search for other papers by M Powell in
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Summary
Tuberculosis (TB) is an important cause of mortality and morbidity across the world. In 2–5% of all cases of systemic TB, the C is affected, with lesions reported in the meninges, cortex and ventricles. Intrasellar tuberculomas, however, are extremely rare. We report the interesting case of a young female patient who presented with secondary hypothyroidism and hyperprolactinaemia. She was treated successfully for pituitary TB. We also highlight and discuss some interesting (and hitherto unreported) endocrine issues. Radiological and histological features and treatment of pituitary TB are discussed using this case as an example.
Learning points
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Intrasellar TB continues to be a rare presentation, but incidence and prevalence are expected to grow with increasing numbers of multidrug-resistant TB and shrinking geographical boundaries across the world.
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Pituitary TB can present with features of a typical adenoma, but has certain radiological and histological features that help to differentiate from an adenoma.
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Patients can present with a variety of endocrine abnormalities at different times.
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The presence of an intrasellar mass in individuals at a high risk of developing TB, or with a previous history of systemic TB, should prompt the diagnosis of pituitary TB. In such individuals, it may be worth considering a trial of anti-tuberculous therapy, before considering surgery.
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Search for other papers by William Drake in
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Summary
A state of insulin resistance is common to the clinical conditions of both chronic growth hormone (GH) deficiency and GH excess (acromegaly). GH has a physiological role in glucose metabolism in the acute settings of fast and exercise and is the only anabolic hormone secreted in the fasting state. We report the case of a patient in whom knowledge of this aspect of GH physiology was vital to her care. A woman with well-controlled type 1 diabetes mellitus who developed hypopituitarism following the birth of her first child required GH replacement therapy. Hours after the first dose, she developed a rapid metabolic deterioration and awoke with hyperglycaemia and ketonuria. She adjusted her insulin dose accordingly, but the pattern was repeated with each subsequent increase in her dose. Acute GH-induced lipolysis results in an abundance of free fatty acids (FFA); these directly inhibit glucose uptake into muscle, and this can lead to hyperglycaemia. This glucose–fatty acid cycle was first described by Randle et al. in 1963; it is a nutrient-mediated fine control that allows oxidative muscle to switch between glucose and fatty acids as fuel, depending on their availability. We describe the mechanism in detail.
Learning points
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There is a complex interplay between GH and insulin resistance: chronically, both GH excess and deficiency lead to insulin resistance, but there is also an acute mechanism that is less well appreciated by clinicians.
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GH activates hormone-sensitive lipase to release FFA into the circulation; these may inhibit the uptake of glucose leading to hyperglycaemia and ketosis in the type 1 diabetic patient.
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The Randle cycle, or glucose–fatty acid cycle, outlines the mechanism for this acute relationship.
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Monitoring the adequacy of GH replacement in patients with type 1 diabetes is difficult, with IGF1 an unreliable marker.
