Corticosteroid and pheo

This interesting topic is suggested by a reader. The relationship between corticosteroid and pheo is multifold and involves several fundamental physiological issues.

Firs of all, the close proximity of the adrenal cortex and adrenal medulla is an intriguing phenomenon. The adrenal glands are small organs. An adrenal gland actually is further divided into two organs, the cortex (secreting corticosteroid) and medulla (where pheo is derived from), each with related but different functions. Why is the adrenal medulla wrapped around by the cortex? Why isn't the medulla located inside other organs, say, the spleen or liver, or a free-standing organ like a ganglion? I can only think of two other organs, pituitary and pancreas, which are also further divided into two organs. In the case of pituitary, anterior and posterior; pancreas, exocrine and endocrine. The question is still unsettled. Existing evidence suggests that the corticosteroid secreted by the adrenal cortex is important in maintaining the medulla what it is. If one takes the cells from the medulla and puts them in culture, those cells automatically differentiate into neuronal cells. If one adds high concentrations of corticosteroid into the culture, the medulla cells will remain neuroendocrine cells and do not differentiate into neuronal cells. As the medulla cells are derived from the neurocrest during embryonic development, it is hypothesized that the migrating neurocrest cells encounter adrenal cortex cells (which provide high concentrations of corticosteroid) and really like them and stay with them. Thus the story of adrenal cortex and adrenal medulla.

Second, corticosteroid stimulates catecholamine production and release from cultured adrenal medulla cells. Corticosteroid increases catecholamine production by upregulating the key enzymes for catecholamine production. The mechanisms for which corticosteroid stimulates catecholamine release are not clear and may not be straightforward.

Third, corticosteroid prepares the target tissues of catecholamines to be responsive to catecholamines. That is why patients with adrenal insufficiency often have low blood pressure even when they have high catecholamine levels.

Lastly, there have been a number of case reports on pheo crisis induced by corticosteroid use. The pheo crisis usually starts a few hours after corticosteroid use. There may be hemorrhage within the pheo. In patients with known pheo or an adrenal tumor of unclear nature, corticosteroid should be avoided if possible. When corticosteroid is used, patients should be closely monitored. In my own experience, pheo crisis by corticosteroid is rare and not a predictable event.

On a separate note, I have been very busy recently. To readers who are used to my quick responses, I may appear to become sloppy. I apologize. I am still following this blog closely but not as frequently as before. Please rest assured that I will respond to your questions, just not as timely.

Have a great Thanksgiving!

Dr. Pheo