Screening for genetic causes of growth hormone hypersecretion

Precision Therapy in Acromegaly Caused by Pituitary Tumors: How Close Is It to Reality?

Acromegaly presents with an enigmatic range of symptoms and comorbidities caused by chronic and progressive growth hormone elevations, commonly due to endocrinologic hypersecretion from a pituitary gland tumor. Comprehensive national acromegaly databases have been appearing over the years, allowing for international comparisons of data, although still presenting varying prevalence and incidence rates. Lack of large-scale analysis in geographical and ethnic differences in clinical presentation and management requires further research. Assessment of current and novel predictors of responsiveness to distinct therapy can lead to multilevel categorization of patients, allowing integration into new clinical guidelines and reduction of increased morbidity and mortality associated with acromegaly. This review compares current data from epidemiological studies and assesses the present-day application of prognostic factors in medical practice, the reality of precision therapy, as well as its future prospects in acromegaly, with a special focus on its relevance to the South Korean population.

Fertility issues in aggressive pituitary tumors

The management of aggressive pituitary adenomas represents a special clinical challenge, and usually involves a combination of surgery, radiotherapy and pharmacological agents to control tumor growth and hormone abnormalities. Fertility is commonly affected in these patients due to compressive effects of the tumor, pituitary hormone dysfunction or as a result of the multiple therapies. The initial approach to restore fertility involves the reduction of tumor volume by the use of dopamine agonists in prolactinomas and by surgery in other pituitary adenomas. Somatostatin analogues are alternative options for GH, ACTH and TSH-secreting tumors. When present, pituitary deficiencies should be appropriately treated, particularly GH deficiency that has been associated with poor pregnancy rates in hypopituitary patients. Other therapies for aggressive pituitary tumors, such as invasive surgery, radiotherapy and temozolamide, may lead to infertility. In such cases, fertility preservation strategies might be considered and discussed with the patient desiring conception before or during treatment. In men and women with hypogonadotropic hypogonadism, administration of gonadotropins or pulse GnRH has resulted in satisfactory pregnancy rates. If spontaneous gestation is not achieved, assisted reproduction techniques can be employed as the last line of treatment. In any context, pre-conception counseling and care are essential as pregnancies in women with aggressive pituitary tumors should always be considered high risk.

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Acromegaly is characterized by increased release of growth hormone (GH) and, consequently, Insulin-Like Growth Factor I (IGF-I), most often by a pituitary adenoma. Prolonged exposure to excess hormone leads to progressive somatic disfigurement and a wide range of systemic manifestations that are associated with increased mortality. Transsphenoidal adenomectomy is the treatment of choice of GH-secreting pituitary tumors but surgical cure is not achieved in around 50% of patients, then adjuvant treatment is necessary. Mortality in acromegaly is normalized with biochemical control and has decreased in the last decade with the increased use of adjuvant therapy. Both GH and IGF-I are currently biomarkers for assessing disease activity in patients with acromegaly. However, discordance between GH and IGF-I results is encountered in a quarter of treated patients. The impacts of such a discrepancy over mortality and morbidity and the risk of biochemical and/or clinical recurrence are unclear. Moreover, despite a good biochemical control, some symptoms persist, leading to a decreased quality of life. Back pain due to vertebral fractures seem to be frequent in these patients and underdiagnosed. In patients with acromegaly, bone mineral density is not a reliable predictor of fracture risk. A more accurate evaluation of bone microstructural alterations associated with GH hypersecretion and vertebral fractures may be provided by new radiological devices analyzing alteration of trabecular microarchitecture, leading to a better prevention. © 2019 Published by Elsevier Masson SAS. All rights reserved. Cet article fait partie du numéro supplément Les Must de l'Endocrinologie 2019 réalisé avec le soutien institutionnel de Ipsen-Pharma.

The 3PAs: An Update on the Association of Pheochromocytomas, Paragangliomas, and Pituitary Tumors

Pituitary adenomas (PA) and pheochromocytomas/paragangliomas (PHEO/PGL) are rare tumors. Although they may co-exist by coincidence, there is mounting evidence that genes predisposing in PHEO/PGL development, may play a role in pituitary tumorigenesis. In 2012, we described a GH-secreting PA caused by an SDHD mutation in a patient with familial PGLs and found loss of heterozygosity at the SDHD locus in the pituitary tumor, along with increased hypoxia-inducible factor 1α (HIF-1α) levels. Additional patients with PAs and SDHx defects have since been reported. Overall, prevalence of SDHx mutations in PA is very rare (0.3-1.8% in unselected cases) but we and others have identified several cases of PAs with PHEOs/PGLs, like our original report, a condition which we termed the 3 P association (3PAs). Interestingly, when 3PAs is found in the sporadic setting, no SDHx defects were identified, whereas in familial PGLs, SDHx mutations were identified in 62.5-75% of the reported cases. Hence, pituitary surveillance is recommended among patients with SDHx defects. It is possible that the SDHx germline mutation-negative 3PAs cases may be due to another gene, epigenetic changes, mutations in modifier genes, mosaicism, somatic mutations, pituitary hyperplasia due to ectopic hypothalamic hormone secretion or a coincidence. PA in 3PAs are mainly macroadenomas, more aggressive, more resistant to somatostatin analogues, and often require surgery. Using the Sdhb ^+/- mouse model, we showed that hyperplasia may be the first abnormality in tumorigenesis as initial response to pseudohypoxia. We also propose surveillance and follow-up approach of patients presenting with this association.

Molecular determinants of the response to medical treatment of growth hormone secreting pituitary neuroendocrine tumors

Acromegaly is a chronic systemic disease mainly caused by a growth hormone (GH)-secreting pituitary neuroendocrine tumor (PitNETs), which is associated with many health complications and increased mortality when not adequately treated. Transsphenoidal surgery is considered the treatment of choice in GH-secreting PitNETs, but patients in whom surgery cannot be considered or with persistent disease after surgery require medical therapy. Treatment with available synthetic somatostatin analogues (SSAs) is considered the mainstay in the medical management of acromegaly which exert their beneficial effects through the binding to a family of G-protein coupled receptors encoded by 5 genes (SSTR1-5). However, although it has been demonstrated that the SST1-5 receptors are physically present in tumor cells, SSAs are in many cases ineffective (i.e. approximately 10-30% of patients with GH-secreting PitNET are unresponsive to SSAs), suggesting that other cellular/molecular determinants could be essential for the response to the pharmacological treatment in patients with GH-secreting PitNETs. Therefore, the scrutiny of these determinants might be used for the identification of subgroups of patients in whom an appropriate pharmacological treatment can be successfully employed (responders vs. non-responders). In this review, we will describe some of the existing, classical and novel, genetic and molecular determinants involved in the response of patients with GH-secreting PitNETs to the available therapeutic treatments, as well as new molecular/therapeutic approaches that could be potentially useful for the treatment of GH-secreting PitNETs.

Acromegaly

Acromegaly is characterized by increased release of growth hormone and, consequently, insulin-like growth factor I (IGF1), most often by a pituitary adenoma. Prolonged exposure to excess hormone leads to progressive somatic disfigurement and a wide range of systemic manifestations that are associated with increased mortality. Although considered a rare disease, recent studies have reported an increased incidence of acromegaly owing to better disease awareness, improved diagnostic tools and perhaps a real increase in prevalence. Acromegaly treatment approaches, which include surgery, radiotherapy and medical therapy, have changed considerably over time owing to improved surgical procedures, development of new radiotherapy techniques and availability of new medical therapies. The optimal use of these treatments will reduce mortality in patients with acromegaly to levels in the general population. Medical therapy is currently an important treatment option and can even be the first-line treatment in patients with acromegaly who will not benefit from or are not suitable for first-line neurosurgical treatment. Pharmacological treatments include somatostatin receptor ligands (such as octreotide, lanreotide and pasireotide), dopamine agonists and the growth hormone receptor antagonist pegvisomant. In this Primer, we review the main aspects of acromegaly, including scientific advances that underlie expanding knowledge of disease pathogenesis, improvements in disease management and new medical therapies that are available and in development to improve disease control.

Heart in Acromegaly: The Echocardiographic Characteristics of Patients Diagnosed with Acromegaly in Various Stages of the Disease

To determine whether the echocardiographic presentation allows for diagnosis of acromegalic cardiomyopathy. 140 patients with acromegaly underwent echocardiography as part of routine diagnostics. The results were compared with the control group comprising of 52 age- and sex-matched healthy volunteers. Patients with acromegaly presented with higher BMI, prevalence of arterial hypertension, and glucose metabolism disorders (i.e., diabetes and/or prediabetes). In patients with acromegaly, the following findings were detected: increased left atrial volume index, increased interventricular septum thickness, increased posterior wall thickness, and increased left ventricular mass index, accompanied by reduced diastolic function measured by the following parameters: E'med., E/E', and E/A. Additionally, they presented with abnormal right ventricular systolic pressure. All patients had normal systolic function measured by ejection fraction. However, the values of global longitudinal strain were slightly lower in patients than in the control group; the difference was statistically significant. There were no statistically significant differences in the size of the right and left ventricle, thickness of the right ventricular free wall, and indexed diameter of the ascending aorta between patients with acromegaly and healthy volunteers. None of 140 patients presented systolic dysfunction, which is the last phase of the so-called acromegalic cardiomyopathy. Some abnormal echocardiographic parameters found in acromegalic patients may be caused by concomitant diseases and not elevated levels of GH or IGF-1 alone. The potential role of demographic parameters like age, sex, and/or BMI requires further research.

AIP limits neurotransmitter release by inhibiting calcium bursts from the ryanodine receptor

Pituitary tumors are frequently associated with mutations in the AIP gene and are sometimes associated with hypersecretion of growth hormone. It is unclear whether other factors besides an enlarged pituitary contribute to the hypersecretion. In a genetic screen for suppressors of reduced neurotransmitter release, we identified a mutation in Caenorhabditis elegans AIPR-1 (AIP-related-1), which causes profound increases in evoked and spontaneous neurotransmitter release, a high frequency of spontaneous calcium transients in motor neurons and an enlarged readily releasable pool of vesicles. Calcium bursts and hypersecretion are reversed by mutations in the ryanodine receptor but not in the voltage-gated calcium channel, indicating that these phenotypes are caused by a leaky ryanodine receptor. AIPR-1 is physically associated with the ryanodine receptor at synapses. Finally, the phenotypes in aipr-1 mutants can be rescued by presynaptic expression of mouse AIP, demonstrating that a conserved function of AIP proteins is to inhibit calcium release from ryanodine receptors.

In this work the authors show that AIP (aryl hydrocarbon receptor-interacting protein), a gene frequently mutated in association with pituitary tumors, regulates neurotransmitter release by inhibiting calcium release from ryanodine receptors.