What is an adrenal adenoma?
An adrenal adenoma is a benign mass in the adrenal gland that sits on top of the kidney. Adrenal adenomas are largely non-functional meaning that it occupies space but does not secrete hormones. However, sometimes benign masses in the adrenal glands can be functional thereby causing high levels of some of the adrenal hormones. Although the exact cause of an adrenal adenoma is unknown in most cases, it is often associated with inherited endocrine diseases. Large tumors and functional adrenal adenomas need to be surgically removed and often does not recur.
Adrenal Adenoma Incidence
The true incidence of an adrenal adenoma is unclear because about 80% of these masses are non-functional. This means it is hormonally silent and does not cause any symptoms. It is discovered incidentally during a CT scan or MRI which is conducted for some other reasons. It is estimated that an adrenal adenoma is present in 1% to 10% of CT scans and MRIs. Since it is discovered incidentally, it is often referred to as an adenoma incidentaloma (AI). It is estimated that about 6% of people over the age of 60 years have an adrenal adenoma that is often only discovered incidentally or post-mortem.
Adrenal Adenoma Pathophysiology
The adrenal glands
The adrenal glands are somewhat triangular shaped glands sitting on the top of each kidney. It has two distinct zones within it – the adrenal medulla and the adrenal cortex. The medulla is the small central portion of the gland. It secretes the hormones epinephrine and norerpinephrine. These hormones are known as catecholamines and can influence heart rate, and affect the size of the lumen of the blood vessels and airways. It mediates the fight or flight stress response.
The outer layer is the adrenal cortex which secretes a number of corticosteroids hormones. These corticosteroids can in turn be divided into the glucocorticoids (like cortisol) and mineralocorticoids (like aldosterone). Glucocorticoids influence the body’s metabolism like the glucose levels, blood pressure and assimilation of nutrients. The mineralocorticoids affect the fluid and electrolyte balance which can influence various processes in the body like blood pressure. Small amounts of other hormones, like the sex hormones, are also secreted by the adrenal glands.
Benign adrenal tumors
An adrenal adenoma is a benign tumor in the adrenal gland. It arises from overgrowth of the adrenal tissue, mainly from the adrenal cortex hence the term adrenal cortical adenoma. When the tumor is within the adrenal medulla then is known as pheochromocytoma. Benign means that it is non-cancerous and must be differentiated from a malignant tumors. The latter, malignancies, are cancerous like an adrenal carcinoma. The cells of a benign tumor are similar to the normal cells of the gland but have just overgrown excessively to form a mass. It does not invade surrounding tissue like a malignancy. Neither does it spread to other parts either through direct infiltration, the lymphatics or bloodstream as is the case with cancer.
Functional or non-functional tumors
About 80% of adrenal adenomas are are non-functional. It is also referred to as hormonally silent. This means that it does not produce and secrete any hormones despite arising from the adrenal gland tissue. However, a small portion of these adrenal tumors are functional. It can secrete hormones and may impact on the normal adrenal gland tissue to increase hormone production. Functional tumors (hormonally active) cause a range of symptoms that indicate the underlying hormone excess while non-functional tumors are largely silent (asymptomatic).
Adrenal Adenoma Causes
The exact cause of adrenal adenoma is often unknown. There appears to be genetic factors involved, either with mutations of chromosomes or inherited genes. An adrenal adenoma is associated with certain inherited disorders like :
- multiple endocrine neoplasia type 1 (MEN-1)
- Beckwith-Weidemann syndrome
- Carney complex
It may also arise with certain genetic disorder that causes an oversecretion of the adrenal hormones. This can cause the tissue of the adrenal gland to enlarge and sometimes in an uncontrollable manner thereby leading to an adrenal adenoma. Despite the link with inherited diseases, it appears that most cases of adrenal adenoma are not associated with any genetic factors and arise spontaneously for no clearly identifiable reason.
Adrenal Adenoma Symptoms
The symptoms largely depend on whether it is a functional or non-functional tumor. Since most adrenal tumors are non-functional there is no excess of adrenal hormones and therefore no clearly evident symptoms, if any at all.
Most functional adrenal adenomas lead to an overproduction of the corticosteroids. An excess of cortisol, the most common occurrence with an adrenal adenoma gives rise to Cushing syndrome. Due to the widespread effects of cortisol, the signs and symptoms may include :
- Striae (pink, purple or brown elongated marks)
- Thinning scalp hair
- Beard hair growth in women (hirsuitism)
- Muscle and bone weakness
- Easy bruising
- Fertility problems
- Hypertension (high blood presure), hyperglycemia (high glucose levels) and hyperlipidemia (high blood fats)
When the mineralocorticoids are produced in excess, the syndrome of hyperaldosteronism (Conn syndrome) is seen. These symptoms include :
- High blood pressure
- Excessive urination
- Muscle weakness
An excess of the male sex hormones presents with various symptoms in both males and females. The most notable is changes in hair growth and acne vulgaris. It may also cause virilization in females as the females sex hormones can cause feminization in males.
Adrenal Adenoma Diagnosis
Most adrenal adenomas are discovered incidentally since it often asymptomatic. This may be through a computed tomography (CT) scan or magnetic resonance imaging (MRI). It is unlikely to be discovered if it is less than 5mm (millimeters) in size. Various biochemical tests should be conducted to verify if there is an excess of any hormones even though there may be no obvious symptoms at the outset. This will help identify the degree to which the adrenal gland is affected and warrant prompt treatment before complications arise.
Benign or Malignant
A CT scan and MRI are very effective imaging studies to identify an adrenal adenoma and can also confirm that it is not a malignancy (cancer). However, a sample should be collected when it a malignancy is suspected or even with a functional tumor to verify whether it is cancer or not. This is done through an adrenal FNA (fine needles aspiration) where a needle is guided into the adrenal gland and a small sample is collected. The tissue sample is then examined under a microscope to note the difference in cell structure and other characteristics.
Adrenal Adenoma Treatment
Non-functioning adrenal adenomas that are less than 3cm (centimeters) are usually not treated. However, close monitoring is important with annual investigations to confirm that it is not increasing in size. A functional adrenal adenoma or non-functional adrenal adenoma that is greater than 3cm in size warrants the need for surgery. The adrenal gland is surgically removed and this is known as as an adrenalectomy. Laparoscopic procedures are preferable as it is less invasive, has fewer complications and a faster recovery time.