1. Linda Is Experiencing Signs and Symptoms Similar to Those of Cushing Disease Or Cushing

Chapter 17

1. Linda is experiencing signs and symptoms similar to those of Cushing disease or Cushing syndrome. This disease results from excessive ACTH secretion that causes elevations in cortisol secretion. Prednisone is a cortisol agonist and would therefore also stimulate signs and symptoms of elevated cortisol. 2. Linda would not exhibit the symptoms directly related to the elevated ACTH observed in Cushing disease and Cushing syndrome—elevation in cortisol and hyperpigmentation of the skin. 3. Long-term treatment with prednisone could also cause Linda to experience acne, trunkal obesity, transient weight gain, facial flushing, thinning of the skin, increased susceptibility to bruising, decreased wound healing, muscle wasting, limb weakness, the development of a "buffalo hump," increased susceptibility to infection, hypertension, and some psychological effects. 4. The dose of prednisone that Linda has been receiving could have induced down- regulation of the cortisol receptors. In order to prevent lack of response to the normally secreted cortisol, the prednisone needs to be withdrawn gradually to allow for an increase in cortisol receptor numbers sufficient to mediate cellular responses to cortisol. 5. The high level of prednisone would act through negative feedback to decrease the secretion of corticotropin-releasing hormone (CRH) and therefore ACTH. The decrease in ACTH would decrease the endogenous secretion of cortisol. 6. Addison disease results from hyposecretion of cortisol. The lack of cortisol negative feedback would cause an increase in CRH and subsequently ACTH. 7. This would be type II diabetes mellitus (NIDDM), because hyperglycemia triggers insulin hypersecretion, and this, in turn, causes cells to down-regulate their insulin receptors and develop insulin resistance. 8. GH hypersecretion is associated with hypertrophy of the pituitary gland, resulting in enlargement of the sella turcica, the gland’s bony enclosure in the sphenoid bone. 9. Antidiuretic hormone normally stimulates the thirst centers in the hypothalamus. In patients with SIADH, the increased ADH stimulates the thirst center even though the person is overhydrated. 10. Theophylline would prolong the cellular responses to hormones activating adenylate cyclase because the cAMP produced by adenylate cyclase would not be metabolized normally. Since caffeine would have an effect similar to that of theophylline, the doctor would most likely recommend that the patient reduce or eliminate caffeine consumption.