Disorders of the endocrine system

Primary versus Secondary Disorders

• • A primary disorder means dysfunction originating in the endocrine gland itself, either hyper- or hypo-function. Examples of a primary dis-order include:

    • excess cortisol from an adrenal adenoma (Conn’s disease)

    • decreased thyroid secretion (Hashimoto’s thyroiditis)

    • reduced ADH secretion (central diabetes insipidus)

  • A secondary disorder indicates that a disturbance has occurred causing the gland secrete more or less of the hormone. Examples of a secondary disorder include:

    • Cushing disease (pituitary adenoma secreting ACTH) resulting in hypercortisolism

    • a dehydrated patient with elevated plasma osmolality causing high ADH levels

Hypofunction

• • Can be caused by autoimmune disease (e.g., type I diabetes, hypothyroidism, primary adrenal insufficiency, gonadal failure), tumors, hemorrhage, infection, damage by neoplasms

  • Evaluated by a stimulation test

  • Hypothalamic hormones test anterior pituitary reserve

  • Injection of the pituitary trophic hormone (e.g., ACTH) tests target gland reserve.

  • Failure of growth hormone release after arginine injection

Hyperfunction

• • Caused by hormone-secreting tumors, hyperplasia, autoimmune stimulation, ectopically produced peptide hormones (e.g., ACTH, ADH)

  • Evaluated by a suppression test

  • Failure of glucose to suppress growth hormone diagnostic for acromegaly

  • Failure of dexamethasone (low dose) to suppress cortisol diagnostic for hypercortisolism

  • Multiple endocrine neoplasia (MEN) represents a group of inheritable syndromes characterized by multiple benign or malignant tumors.

    • o MEN 1: hyperparathyroidism, endocrine pancreas, and pituitary adenomas

    • o MEN 2A: medullary carcinoma of the thyroid, pheochromocytoma, hyperparathyroidism

    • o MEN 2B: medullary carcinoma of the thyroid, pheochromocytoma, hyperparathyroidism typically absent.

Gland Structure and Size

• • When an endocrine gland does not receive its normal stimulus, it generally undergoes a reversible atrophy.

    • Long-term high doses of glucocorticoids suppress the ACTH-adrenal axis. Withdrawal of therapy can require up to a year for complete recovery.

  • Overstimulation of endocrine tissue can cause cell proliferation or hypertrophy in addition to hormone overproduction.

    • In Graves’ disease, overstimulation of the thyroid tissues causes cell proliferation and this polyclonal expansion creates a goiter in addition to hyperthyroidism.

  • Tumors, which are generally monoclonal expansions, may also create a hyperfunction. Others produce little if any hormone but are still disease-producing because of the compressive (mass) effect of the additional tissue.