Chronically-high levels of glucocorticoids like cortisone can also be the result

Question

Chronically-high levels of glucocorticoids like cortisone can also be the result of an overactive pituitary gland or adrenal gland. How can increased activity of each of these glands lead to an overproduction of glucocorticoids?

To determine which gland is abnormally over-active in a particular patient, doctors can use the drug dexamethasone, a synthetic glucocorticoid that blocks ACTH release. If administration of dexamethasone has no effect on cortisone levels in the blood, what would this suggest? Explain your logic.

Explanation / Answer

1. The adenohypophysis part of the pituitary produces adrenocorticotropic hormone(ACTH) (with cell type as corticotroph) which controls the secretion of adrenal cortex hormones which are categorized into three categories such as mineralocorticoids, glucocorticoids and sex corticoids.

if the pituitary becomes overactive i.e. if secrete an excessive amount of ACTH , if will thereby affect the adrenal cortex hormones and may be it can lead to excessive or over production of glucocorticoids. similarly the overactive adrenal gland will secrete excessive amounts of the hormones it produces and if it secrete the excessive amount of glucocorticoids the disease can be called as cushing's syndrome where a tumor of adrenal cortex may secrete too much cortisol (over production of glucocorticoid) leading to high blood sugar, appearance of sugar in the urine, wasting of limb muscle, rise in plasma sodium ion concentration or high blood pressure.

2. the abnormal results with low dose means that there is abnormal release of the cortisol. it can be beacuse of 3 reasons:

if with the normal low dosage of the drug there is no effect i.e. no decrease in the blood cortisol level, but with higher dosages if administered to the patient's body and you find a decrease in blood cortisol level, it is the pituitary tumor causing cushing syndrome.

if there is no effect with high and low doses , with ACTH levels increased , it is due to the ectopic cushing syndrome.

if the low dose has no decrease effect of blood cortisol and have low ACTH levels then it is due to adrenal tumors.

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