Adrenal insufficiency
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ayeesha Kattubadi, M.B.B.S[2]
Overview
Historical Perspective
Thomas Addison in 1885 first defined adrenal insufficiency as a disorder of impaired adrenocortical function leading to deficiency in glucocorticoids, mineralocorticoids, and adrenal androgens. The most common causes of primary adrenal insufficiency have been constantly evolving. In the 1920s, the most common cause was tuberculosis, whereas in the 1950s it is autoimmune polyglandular syndrome. [1]
Classification
Adrenal insufficiency is classified based on the location of the pathology into: [2]
In Primary adrenal insufficiency, the pathology lies in the adrenal glands leading to decreased production of cortisol and aldosterone.The most common cause of primary adrenal insufficiency is autoimmune adrenalitis. In secondary adrenal insufficiency, the pathology lies in the pituitary gland leading to reduced ACTH production, whereas in tertiary adrenal insufficiency the pathology lies in the hypothalamus leading to reduced CRH production. The most common cause of tertiary adrenal insufficiency is chronic glucocorticoid therapy. Secondary and tertiary adrenal insufficiency together are categorised into central adrenal insufficiency. The following table summaries the causes of adrenal insufficiency.
Causes of adrenal insufficiency | ||
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Primary adrenal insufficiency (Addison's disease) |
Secondary adrenal insufficiency | Tertiary adrenal insufficiency |
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Pathophysiology
The pathogenesis of adrenal insufficiency varies based on the etiology as follows: [3]
Autoimmune adrenalitis: Humoral as well as cell mediated immune mechanisms attack various enzymes involved in the synthesis of adrenal cortical enzymes. Strong genetic association has bene seen with HLA DR3/DQ2 and DR4/DQ8. On gross anatomy the adrenal gland is atrophied with preservation of adrenal medulla. Histopathology shows lymphocytic infiltration with fibrosis of the parenchyma. The patients are asymptomatic until up to 90% of the cortex is destroyed. Autoantibodies against 21-hydroxylase, an essential enzyme required in the biosynthesis of steroid hormones of the adrenal cortex are seen.
- Isolated autoimmune adrenalitis accounts for 30-40% cases.
- Autoimmune Polyglandular Syndrome (APS) account for 60-70%. Which is further subclassified as follows:
Autoimmune Polyglandular Syndrome Type 1 (APS type 1): Exhibits autosomal recessive mode of inheritance. It is also known as Autoimmune Polyendocrinopathy-Candidiasis-Ectodermal Dystrophy (APECED). Caused due to mutations in the autoimmune regulator gene (AIRE). Apart from adrenal insufficiency it presents with chronic mucocutaneous candidiasis, hypoparathyroidism, total alopecia.
Autoimmune Polyglandular Syndrome Type 2 (APS type 2): It is more common than APS type 1 and has polygenic inheritance. Strong association has been shown with HLA DR3 of MHC. Apart from adrenal insufficiency it presents with autoimmune thyroiditis, vitiligo, premature ovarian failure, type 1 diabetes mellitus, pernicious anemia.
X linked Adrenoleukodystrophy(X-ALD): X-ALD occurs due to mutations in the peroxisomal ATP-binding cassette (ABC) transporter encoded by the ABCD1 gene. Disruption of this transport protein leads to the accumulation of Very Long Chain Fatty Acids (VLCFA). Male patients usually present in childhood or adolescence, whereas heterozygous females present between 40-50 years. The phenotypic expression is variable and can present as pre-symptomatic, cerebral inflammatory demyelination, myelopathy, adrenal insufficiency. The lifetime prevalence of adrenal insufficiency is 80% in males, with the highest risk being in the first decade. Adrenal insufficiency is extremely rare in females. [4]
Chronic glucocorticoid use: Tertiary adrenal insufficiency induced by chronic oral and inhaled glucocorticoid use is the most common cause of adrenal insufficiency. Exogenous glucocorticoid use leads to the feedback inhibition of the HPA axis leading to reduced synthesis of CRH and ACTH by hypothalamus and pituitary. As a consequence of reduced ACTH, the adrenal cortex slowly loses the ability to synthesize cortisol. The mineralocorticoid synthetic function of the adrenal cortex is retained as it depends on RAAS. HPA axis function recovers quickly if glucocorticoids were used for less than 10-14 days. If glucocorticoids were used for >2weeks, weaning and assessment of HPA integrity are recommended. In some cases the HPA axis may remain suppressed for as long as 6-12 months after glucocorticoid withdrawal. [5]. [6]
The other causes of adrenal insufficiency are due to the destruction of the adrenal, pituitary or hypothalamus due to various causes as mentioned in the table above.
Causes
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References
- ↑ "www.elsevier.es".
- ↑ "Adrenal Insufficiency - Endotext - NCBI Bookshelf".
- ↑ "Adrenal Insufficiency - StatPearls - NCBI Bookshelf".
- ↑ Berger J, Forss-Petter S, Eichler FS (2014). "Pathophysiology of X-linked adrenoleukodystrophy". Biochimie. 98: 135–42. doi:10.1016/j.biochi.2013.11.023. PMC 3988840. PMID 24316281.
- ↑ Younes AK, Younes NK (2017). "Recovery of steroid induced adrenal insufficiency". Transl Pediatr. 6 (4): 269–273. doi:10.21037/tp.2017.10.01. PMC 5682381. PMID 29184808.
- ↑ "Glucocorticoid Therapy and Adrenal Suppression - Endotext - NCBI Bookshelf".