As of September 1, 2021, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is the virus responsible for the coronavirus disease 2019 (COVID-19), has infected over 219 million and caused the deaths of over 4.5 million worldwide. Although COVID-19 has been traditionally associated with its ability to cause varied symptoms resembling acute respiratory distress syndrome (ARDS), emerging scientific evidence has demonstrated that SARS-CoV-2 causes much more damage beyond its effects on the upper respiratory tract.
To this end, in a recent study published in Reviews in Endocrine and Metabolic Disorders, the researchers discuss the extra-pulmonary manifestations of COVID-19.
Study: COVID-19 and hypopituitarism. Image Credit: Lightspring / Shutterstock.com
Risk factors for severe COVID-19
It is now a well-known fact that the likelihood of people falling severely ill or dying from COVID-19 is increases if these individuals are obese, or have certain comorbidities like diabetes mellitus (DM), vitamin D deficiency, and vertebral fractures (VFs).
Any abnormality in the pituitary gland may lead to metabolic disorders, impaired immunity, and a host of other conditions that also make the body susceptible to infections. Since such conditions are common in patients with COVID-19 as well, it has been hypothesized that there might be a relationship between COVID-19 and pituitary gland disorders.
On the other hand, researchers have also observed that COVID-19 causes increased severity of pituitary-related disorders, and even pituitary apoplexy, which is a condition defined as internal bleeding or impaired blood supply in the pituitary gland. A group of Italian researchers has reviewed this bidirectional relationship between the pituitary gland abnormalities and COVID-19 in their study recently published in Reviews in Endocrine and Metabolic Disorders.
The link between pituitary gland abnormalities and COVID19
The pituitary gland releases hormones that regulate and control some of the most important functions of the body like growth, metabolism, energy levels, bone health, mood swings, vision, reproduction, and immunity, to name a few. The inability of the pituitary gland to release one or more of these hormones is known as ‘hypopituitarism.’ Factors responsible for hypopituitarism include traumatic brain injury, pituitary adenomas (tumors), genetic mutations, as well as infiltrative and infectious diseases.
Hypopituitarism can lead to severe cases of DM, growth hormone deficiency (GHD), abnormal lipid profile, obesity, arterial hypertension, and immune dysfunctions. Interestingly, similar consequences of COVID-19 have also been reported.
SARS-CoV-2 infects the human body by binding to a special class of receptors known as the angiotensin-converting enzyme 2 (ACE2) receptors. These receptors are located in the endothelial linings of most organs like the brain, heart, lungs, kidneys, intestine, liver, and pancreas, among others. The main function of the ACE2 receptors is binding to specific target molecules to maintain the renin-angiotensin system that is crucial for regulating dilation of blood vessels, as well as maintain blood glucose levels, the immune system, and homeostasis.
Therefore, SARS-CoV-2 binding to these ACE2 receptors facilitates the entry of this virus into all the organs that have these receptors, thus leading to the ability of SARS-CoV-2 to cause widespread damage in the body. Upon entry into the pancreas, for example, SARS-CoV-2 can inhibit ß-cells function, which worsens hyperglycemia and increases the risk for acute diabetic complications.
Similarly, the presence of ACE2 receptors in brain tissues may cause invasion into the pituitary gland and lead to pituitary apoplexy. The entry of SARS-CoV-2 into the brain can also cause neurological damage in infected patients, which may account for some of the common neurological complaints of COVID-19 including headaches, confusion, dysgeusia, anosmia, nausea, and vomiting.
Study findings
Hypopituitarism leading to metabolic syndrome has been scientifically linked to higher mortality in COVID-19 patients. In fact, the presence of a single metabolic syndrome component has been observed to double the risk of death by COVID-19. This risk was even higher among patients with DM and hypertension.
There was also an increased incidence of VFs in COVID-19 patients with hypopituitarism. Hence, patients with DM, obesity, hypertension, and chronic inflammatory disease, are all at an increased risk of poor outcomes and death in COVID-19.
Arterial hypertension is a common finding in adults with GHD, which is another consequence of hypopituitarism. Hypopituitarism also causes adrenal insufficiency, a condition that is primarily managed with glucocorticoids and hormonal replacement therapies.
Notably, patients with COVID-19 are often treated for prolonged periods with high-dose exogenous glucocorticoids, which is a class of steroids that suppress some activities of the immune system. This treatment approach may result in suppression of the hypothalamic-pituitary–adrenal axis that can lead to adrenal insufficiency.
Hypogonadism is another aspect of pituitary insufficiency that predisposes patients, especially males, to COVID-19. Evidence shows that males with hypogonadism were more frequently affected by metabolic syndrome.
Pituitary apoplexy, albeit rare, has also been linked to COVID-19, especially in patients with pituitary adenomas and those who are being treated with anticoagulant therapy. This may be because the pituitary gland becomes overstimulated during an infectious disease, which may increase pituitary blood demand and lead to sudden infarction precipitating acute apoplexy.
This phenomenon has also been shown in patients suffering from infectious diseases that cause hemorrhagic fevers. Taken together, pituitary apoplexy complicates treatment and management procedures in COVID-19 patients.
Despite the use of steroids in COVID-19 patients, there have been no contraindications for vaccination in such patients. However, those on extensive hormonal therapies need constant monitoring for best results.
Implications
The pituitary gland acts like a double-edged sword for COVID-19. On one end, hypopituitarism predisposes patients to metabolic disorders like DM, obesity, and VFs, all of which are known risk factors for COVID-19.
On the other hand, COVID-19 may cause direct or indirect damage to the pituitary glands by entering the brain and inducing unfavorable vascular events – though evidence on this remains lesser in comparison to that of hypopituitarism. Ultimately, the researchers of the current study conclude that managing patients with hormonal insufficiencies optimally with steroids is likely to improve outcomes in severe COVID-19.
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