Hormonal Dysfunction in Male Infertility -Diagnosis and Treatment !

Male Infertility:

Treatment of infertility-related hormonal dysfunction in men requires an understanding of the hormonal basis of spermatogenesis. The best method for accurately determining male androgenization status remains elusive. Treatment of hormonal dysfunction can fall into two categories — empirical and targeted. Empirical therapy refers to experience-based treatment approaches in the absence of an identifiable etiology. Targeted therapy refers to the correction of a specific underlying hormonal abnormality.

Since the first case reports in 1910 of testicular atrophy after canine hypophysectomy, the hormonal basis of human reproduction has been an area of evolving investigation. An array of treatment modalities are available for hormonal dysfunction in the setting of male infertility, but the diagnosis of such dysfunction and its treatment is often empirical, or guided by the clinician's judgement, and can be open to interpretation. Our ability to understand the intra testicular hormonal environment and its effect on spermatogenesis is limited by current methods of routine clinical investigation.

Investigations into female infertility benefit from reliance on objective, verifiable outcomes such as ovulation, biochemical pregnancy, and clinical pregnancy. Meanwhile, the male counterpart has been hampered by the necessary dependence on bulk seminal parameters, which are notoriously poor predictors of fertility potential. Perhaps the only truly reliable semen analysis is one indicating azoospermia and that is where the most exciting clinical outcomes research has focused.

This review article describes and discusses the pathophysiology, diagnosis, and treatment of fertility-associated male hormonal dysfunction.

• Oestradiol is the principal mediator of negative feedback on the hypothalamic–pituitary axis, which illustrates the influence of selective oestrogen receptor modulators and aromatase inhibitors on male hormonal parameters

• Serum hormonal assays are unreliable indicators of intratesticular androgen levels, and the best approach for determining male androgen status remains elusive

• Follicle-stimulating hormone and inhibin B are markers of spermatogenesis and their relative values in the setting of an intact hypothalamic–pituitary–gonadal axis provide important information about testicular function

• Targeted hormonal therapy corrects specific hormonal dysfunctions, empirical hormonal therapy is employed when no underlying cause is identified and the evidence for empirical therapy is dependent on the type of medication used

• A return of sperm to the ejaculate or successful surgical sperm retrieval among men with azoospermia owing to spermatogenic dysfunction are the most objective indicators of outcomes of hormonal therapy

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A Primeview on Sickle Cell Disease !

Primeview:

Sickle cell disease (SCD) is a group of inherited disorders caused by mutations in HBB, which encodes haemoglobin subunit β. Haemoglobin molecules that include mutant sickle β-globin subunits can polymerize; erythrocytes that contain mostly haemoglobin polymers assume a sickled form and are prone to haemolysis. Other pathophysiological mechanisms that contribute to the SCD phenotype are vaso-occlusion and activation of the immune system. SCD is characterized by a remarkable phenotypic complexity. Common acute complications are acute pain events, acute chest syndrome and stroke; chronic complications (including chronic kidney disease) can damage all organs. Hydroxycarbamide, blood transfusions and haematopoietic stem cell transplantation can reduce the severity of the disease. Early diagnosis is crucial to improve survival, and universal newborn screening programmes have been implemented in some countries but are challenging in low-income, high-burden settings.

Sickle cell disease (SCD) is an umbrella term that defines a group of inherited diseases (including sickle cell anaemia (SCA), HbSC and HbSβ-thalassaemia) characterized by mutations in the gene encoding the haemoglobin subunit β (HBB). Haemoglobin (Hb) is a tetrameric protein composed of different combinations of globin subunits; each globin subunit is associated with the cofactor haem, which can carry a molecule of oxygen. Hb is expressed by red blood cells, both reticulocytes (immature red blood cells) and erythrocytes (mature red blood cells). Several genes encode different types of globin proteins, and their various tetrameric combinations generate multiple types of Hb, which are normally expressed at different stages of life — embryonic, fetal and adult. Hb A (HbA), the most abundant (>90%) form of adult Hb, comprises two α-globin subunits (encoded by the duplicated HBA1 and HBA2 genes) and two β-globin subunits.

A single nucleotide substitution in HBB results in the sickle Hb (HbS) allele βS; the mutant protein generated from the βS allele is the sickle β-globin subunit and has an amino acid substitution. Under conditions of deoxygenation (that is, when the Hb is not bound to oxygen), Hb tetramers that include two of these mutant sickle β-globin subunits (that is, HbS) can polymerize and cause the erythrocytes to assume a crescent or sickled shape from which the disease takes its name. Hb tetramers with one sickle β-globin subunit can also polymerize, albeit not as efficiently as HbS. Sickle erythrocytes can lead to recurrent vaso-occlusive episodes that are the hallmark of SCD. SCD is inherited as an autosomal codominant trait; individuals who are heterozygous for the βS allele carry the sickle cell trait (HbAS) but do not have SCD, whereas individuals who are homozygous for the βS allele have SCA. SCA, the most common form of SCD, is a lifelong disease characterized by chronic haemolytic anaemia, unpredictable episodes of pain and widespread organ damage.

This primeview focuses on SCA and aims to balance such remarkable advances with the key major challenges remaining worldwide to improve the prevention and management of this chronic disease and ultimately to discover an affordable cure.

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Genetics of Coronary Artery Disease: Discovery, Biology and Clinical Translation !

Genetics

Coronary artery disease is the leading global cause of mortality. Long recognized to be heritable, recent advances have started to unravel the genetic architecture of the disease. Common variant association studies have linked approximately 60 genetic loci to coronary risk. Large-scale gene sequencing efforts and functional studies have facilitated a better understanding of causal risk factors, elucidated underlying biology and informed the development of new therapeutics. Moving forwards, genetic testing could enable precision medicine approaches by identifying subgroups of patients at increased risk of coronary artery disease or those with a specific driving pathophysiology in whom a therapeutic or preventive approach would be most useful.

• Coronary artery disease is a heritable disorder that remains the leading cause of global mortality despite advances in treatment and prevention strategies. Human genetics studies have started to unravel the genetic underpinnings of this disorder.
• Gene discovery efforts have rapidly transitioned from family-based studies (for example, those that led to the discovery of familial hypercholesterolaemia) to large cohorts that facilitate both common and rare variant association studies.
• Common variant association studies have confirmed ∼60 genetic loci with a robust association with coronary disease, the majority of which are of modest effect size and in non-coding regions. Rare variant association studies have linked inactivating mutations in at least nine genes with risk of coronary artery disease.
• Human genetics and large-scale biobanks can facilitate drug development for coronary artery disease by highlighting causal biology and helping to understand the phenotypic consequences of lifelong deficiency of a given protein.
• Genomic medicine may provide patients and their health care providers with genetic data that will aid in coronary artery disease prevention and treatment.
• Genome editing to introduce mutations that are protective against coronary artery disease into the population could prove curative with a one-time injection, although substantial additional work is needed to confirm efficacy and safety, and to address the underlying ethics.

Observational epidemiology and translational research efforts have led to significant progress in improving the understanding of the pathophysiology underlying coronary artery disease (CAD). Prevention and treatment strategies developed on the basis of this knowledge led to a >50% decrease in age-adjusted CAD mortality rate in the United States between 1980 and 2000. However, despite these advances, CAD remains the leading global cause of mortality. Current predictions estimate that more than 900,000 individuals in the United States will suffer a myocardial infarction (heart attack) or die of CAD this year.

This review outlines research efforts to understand the genetic drivers of CAD, the role of human genetics in catalysing CAD drug discovery efforts and the promises and challenges of integrating genetic information into routine clinical practice.

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The Pathophysiology of Defective Proteostasis in the Hypothalamus — From Obesity to Ageing

Hypothalamic dysfunction has emerged as an important mechanism involved in the development of obesity and its comorbidities, as well as in the process of ageing and age-related diseases, such as type 2 diabetes mellitus, hypertension and Alzheimer disease. In both obesity and ageing, inflammatory signalling is thought to coordinate many of the cellular events that lead to hypothalamic neuronal dysfunction. This process is triggered by the activation of signalling via the toll-like receptor 4 pathway and endoplasmic reticulum stress, which in turn results in intracellular inflammatory signalling. However, the process that connects inflammation with neuronal dysfunction is complex and includes several regulatory mechanisms that ultimately control the homeostasis of intracellular proteins and organelles (also known as 'proteostasis'). This Review discusses the evidence for the key role of proteostasis in the control of hypothalamic neurons and the involvement of this process in regulating whole-body energy homeostasis and lifespan.

Key points

• Specialized neurons of the hypothalamus control caloric intake and energy expenditure in response to hormonal, nutritional and neural signals that reflect the energy stores in the body
• Malfunction of the hypothalamus occurs in obesity and ageing, which leads to an imbalance between caloric intake and energy expenditure resulting in positive energy balance and reduced lifespan
• The excessive consumption of certain nutrients and ageing affect different aspects of proteostasis in selected neurons of the hypothalamus, contributing to neuronal dysfunction in obesity and ageing
• Inflammation is one of the most important outcomes of disturbed proteostasis to occur in the hypothalamus during obesity and ageing
• Several genetic and pharmacological approaches used to correct the defects of proteostasis and reduce inflammation have proven effective in reducing obesity and increasing lifespan in experimental models

Read more: The Pathophysiology of Defective Proteostasis in the Hypothalamus — From Obesity to Ageing

Figure 1: Control of energy balance and lifespan by the hypothalamic network. Neurons of the
medium hypothalamus respond to systemic signals of whole-body energy status. Blood levels of
insulin fluctuate acutely in response to carbohydrates present in food and chronically in response
to increased adiposity.

Source: Nature Reviews Endocrinology

Seeking novel drug targets for Autism

Genetic discoveries have invigorated autism research and raised the possibility of finding drug targets based on autism’s underlying pathophysiology, rather than merely treating symptoms.

An experimental group of drugs works wonders in a mouse-model of fragile X syndrome, the most common single-gene cause of autism. The drugs, which calm overactive metabotropic glutamate receptors (mGluRs) in the brain, restore social sniffing behaviour to normal levels, boost learning and memory, and reduce seizures related to the syndrome. Yet despite being the most promising new strategy for treating autism, these drugs are floundering once they reach human subjects.

The obscurity of the causes of autism means that doctors have little to offer the one in 100 people affected worldwide. Intensive behavioural therapies help some, but current medicines are limited to two drugs, risperidone and aripiprazole, used to treat aggression and irritability.

Read more: Seeking novel drug targets for Autism

An electroencephalogram measures brain connectivity, which, when combined with other measures,
may help delineate people with autism into subgroups with their own distinct biology

Source: SciencePhotoLibrary