Hyperplasia is a term that implies an increase in the number of normal cells in a gland or other tissue. Sometimes the cells themselves are also enlarged, or hypertrophic. Tissues can be hypertrophic without being hyperplastic.
Adrenal hyperplasia can be due to primary causes, related to some problem with the adrenal glands, or due to secondary causes when some other distant condition is causing the adrenal hyperplasia.
Adrenal hyperplasia due to any one of the inherited enzyme defects associated with congenital adrenal hyperplasia (CAH) is an example of primary hyperplasia. Primary pigmented nodular adrenocortical disease is another genetic cause of hyperplastic adrenal glands. We will cover these and other causes in subsequent reports.
Adrenal hyperplasias due to ACTH-secreting pituitary tumors or neuroendocrine tumors located elsewhere are described as secondary in nature.
Hyperplasia is often, but not always, associated with nodular changes in one or both adrenal glands. The nodules may range in size from microscopic to several centimeters in size. Some can be quite massive.
Hyperplasia often involves both adrenal glands. Sometimes, only one gland seems to be involved. In my experience, half of these patients with unilateral disease will later develop hyperplasia in their other gland.
Hyperplasia may be associated with normal hormone production, subtle or overt excess production of adrenal androgens, aldosterone, or cortisol, and even hormone deficiency states which may, rarely, even be associated with excess amounts of functional hormones, i.e., hormones with mineralocorticoid activity.
Adrenal enlargement due to other conditions may be mistaken for hyperplasia. Some of the mimics include metastases from cancers that begin elsewhere, infiltrative disorders (fungal infections), and other infections (tuberculosis), etc.
The so-called limbs of the adrenal glands are usually 2-3 mm thick. I consider thickness greater than 5 mm as likely abnormal and especially in patients with clinical or biochemical findings suggestive of adrenal hormone excess. Radiologists often do not report hyperplasia unless the adrenal gland thickness exceeds 10-15 mm. I find this to be too restrictive as I’ve seen legions of patients with endocrine disorders due to hyperplasia with adrenal glands that were distinctly abnormal but were called “normal” by the radiologist interpreting imaging studies. It’s quite important to correlates radiographic and biochemical findings with other clinical data.
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