Case Studies – Endocrine System

The Case of the Wall Street Woodsman

Learning Objectives

  1. List hormones biosynthesized and released from the adrenal cortex.
  2. Describe actions of glucocorticoids on the immune system white blood cells and on proteins of the body.
  3. Describe the action of mineralcorticoids (such as aldosterone) on the kidney and on blood pressure.
  4. Describe the regulation of adrenal cortex function by way of the pituitary gland and negative feedback from adrenal cortex products.
  5. Explain how exogenous administration of adrenal cortex products will affect pituitary gland stimulation of the adrenal cortex.
  6. Discuss why sudden withdrawal of exogenously administered adrenal cortex products can be dangerous.

Case Presentation

Mr. Tanuli, a Wall Street stockbroker, went on a camping trip about a month ago. While vacationing he contracted a severe case of poison ivy – his skin erupted in a severe contact dermatitis, for which a doctor living near the campsite prescribed Prednisone (a glucocorticoid [corticosteroid]) 50 mg/day. The doctor told Mr. Tanuli to taper (slowly diminish in dose) the dose 10 mg/day every 4 days. The doctor also gave Mr. Tanuli some cortisone cream to apply to the affected skin sites. Mr. Tanuli’s vacation was cut short, as he had his fill of the outdoors. Several days later he returned to New York. The dermatitis cleared up in about a week.

One month after returning to New York, Mr. Tanuli was in a motorcycle accident. A friend had introduced Mr. Tanuli to dirt-bike motorcycling. Mr. Tanuli was severely injured. He suffered internal organ damage and a concussion. Upon admittance to the emergency room, Mr. Tanuli’s blood pressure was quite low – 80/50.

During surgery the operating room (OR) team had difficulty maintaining his blood pressure. After recovering from the surgery, the surgeon questioned Mr. Tanuli on medications he had been taking. Mr. Tanuli told his surgeon that he had been taking Prednisone pills, 5 mg/day, for the past two months. Mr. Tanuli explained that he had forgotten that he was supposed to cut down on his dose of the pills over time. He had gotten a refill of the prescription and had kept taking the pills, up until two days before the accident, when he remembered that the doctor who prescribed the pills had told him he was to phase out the dosage. The surgeon understood immediately why his OR team had difficulty maintaining Mr. Tanuli’s blood pressure.

Case Background

The adrenal gland cortex makes and releases about 50 different steroid molecules, but there are only three classes of molecules produced in significant amounts – glucocorticoids, mineralocorticoids, and sex steroids. The pituitary gland stimulates and maintains the adrenal cortex by releasing ACTH (AdrenoCorticoTropin Hormone) into the blood, which then interacts with adrenal cortex cellular receptors (Figure 1). ACTH stimulates adrenal cortex cells to produce an active esterase enzyme that converts cholesterol to pregnenolone, the common precursor molecule for all mammalian steroid hormones. If inadequate ACTH stimulation of the adrenal cortex occurs, resulting in decreased pregnenolone synthesis, production of all adrenal cortex products will be reduced.

ACTH is released when adrenal gland cortex production of glucocorticoids, present in the bloodstream is low, or when the body is faced with a stressful (fight-or-flight) situation. When adrenal cortex production of glucocorticoids is adequate or elevated, the pituitary gland responds by suppressing ACTH release.

Glucocorticoids (cortisol, cortisone, hydrocortisone, hydroxycortisone) inhibit white blood cell function and cause generalized catabolism of molecules in the body. Generalized catabolism (proteolysis, lipolysis, glycogenolysis) mobilizes basic nutrient molecules (amino acids, fatty acids, sugars) for sites of the body that might need them – such as wound sites or a broken bone. Inhibition of WBC function prevents excessive inflammation during a stressful situation. Commercially available glucocorticoids are available by prescription and as over-the-counter medications to treat inflammation (dermatitis, arthritis, etc).

Mineralocorticoids, such as aldosterone, are designed to maintain body blood pressure. They stimulate urinary sodium transport back into the bloodstream. Because sodium ion (Na+) is the major extracellular osmole (because of cellular Na+K+ATPase transport pumps constantly pumping Na+ out of cells to the extracellular environment), sodium is the main determinant of blood osmolality and hence blood fluid volume (blood pressure), because water will be drawn to areas of high osmolality. The adrenal cortex mineralocorticoids thus help the body maintain not only minute-to-minute blood pressure, but also blood pressure during stressful situations.

Finally it is worth noting that all adrenal cortex hormones have some overlap in function. Glucocorticoids have some mineralocorticoid activity. Mineralocorticoids have some glucocorticoid activity. However, each class of adrenal cortex hormone does have a dominant biological action, as discussed.

Fig. 1. Interacctions among te pituitary, nervous system, and adrenal glands, CRF = Corticotropin Releasing Factor, ACTH = Adrenocorticotropic Hormone, ANS = Autonomic Nervous System.

Questions

  1. What is the basis by which glucocorticoids help to treat contact dermatitis (such as poison ivy)? ______

______

  1. Is there anything unusual in the history of Mr. Tanuli’s prednisone medication, specifically regarding his discontinuance of the prednisone? ______Explain. ______

______

  1. Why did Mr. Tanuli’s body have difficulty maintaining normal blood pressure following his accident? ______

______

4.What organ system of his body was a set-up for malfunctioning the day before the accident? ______

Explain. ______

Case Studies – Endocrine System

The Case of the Bug-Eyed Woman

Learning Objectives

  1. Define hyperthyroidism and hypothyroidism.
  2. State the hormone that normally stimulates the thyroid and the tissue where this hormone originates.
  3. List hormones made by the thyroid gland, their abbreviations, and their actions on body cells.
  4. Explain what LATS stands for, what LATS are, and the effect of LATS on the thyroid gland.
  5. List simple blood tests that can be performed to check for both hyperthyroidism and hypothyroidism What test results would you expect to see for each of these two thyroid disorders?

Case Presentation

Wendy Anderson is a 34-year-old female. She came to the clinic because she had noticed an increasing mass in her neck over the past several months. In addition, Wendy has felt more nervous than normal, felt flushed, experienced heart palpitations, fatigue, and loose stools. Wendy’s friends noticed Wendy staring at them frequently, which Wendy denied. Looking at old photos of Wendy, Wendy and her friends concluded that Wendy’s eyes were appearing larger than normal.

Because of Wendy’s symptoms and signs, her doctor had a high suspicion of a thyroid disorder. He ordered blood drawn to check for serum levels of several hormones related to the thyroid gland. Blood analysis revealed the following: TSH diminished, T3 and T4 elevated.

Case Background

The thyroid gland is normally stimulated to secrete thyroid hormone (T3 and T4) under the influence of thyroid stimulating hormone (TSH). TSH is released from the anterior pituitary gland, travels in the bloodstream, attaches to TSH receptors on thyroid gland cells, and stimulates the thyroid gland cells to make and release T3 and T4 (Figure 2). When blood levels of T3 and T4 are adequate, T3 and T4 attach to receptors on pituitary gland cells and signal the pituitary to decrease the release of TSH; a negative feedback loop is thus created.

T3 and T4 enter virtually all body cells, attaching to cell DNA and stimulating genetic production of enzymes involved in metabolism. The thyroid thus stimulates a rise in the body basal metabolic rate (BMR).

Thyroid function can be determined by the serum measurement of T3, T4, and TSH, as well as by physical examination of a person’s general state. There are more complex thyroid function tests, but a measurement of serum T3, T4, and TSH is sufficient for a general diagnosis.

Hyperthyroidism implies a higher than normal release of T3 and T4 from the thyroid; serum levels of T3 and T4 will be elevated. Hyperthyroidism can be caused by several mechanisms. Cells of the thyroid may produce excess thyroid hormone; such a condition can occur with a tumor of the thyroid, cancerous or noncancerous. A tumor of the pituitary gland cells that produce TSH can lead to excess production of TSH, in which case the thyroid gland would be over-stimulated and would produce excess thyroid hormone. Sometimes antibody-like molecules in the blood directed against the thyroid attach to and stimulate the thyroid gland. These molecules, called LATS (long acting thyroid stimulators), attach the TSH receptors of the thyroid, in effect acting like TSH themselves. Such a condition is called Graves disease. The disorder is autoimmune in nature – the immune system is attacking the thyroid gland, causing a hyperthyroidism.

Figure 2. Hormonal interactions between the anterior pituitary and the thyroid gland.

Questions

  1. How will serum levels of T3, T4, and TSH be affected by a destructive tumor of the anterior pituitary gland cells that make TSH?______Will the affected individual suffer from hyper- or hypothyroidism? Circle one: hyper- hypo-

Why?______

  1. How will serum levels of T3, T4, and TSH be affected by a proliferative tumor of the anterior pituitary gland cells that make TSH? ______Will the affected individual suffer from hyper- or hypothyroidism?Circle one: hyper- hypo-

Why?______

  1. How will serum levels of T3, T4, and TSH be affected by a proliferative tumor of the thyroid gland cells that make T3, T4? ______Why? ______Will the affected individual suffer from hyper- or hypothyroidism? Circle one: hyper- hypo-

Why? ______

  1. How will serum levels of T3, T4, and TSH be affected by a destructive tumor of the thyroid gland cells that make T3, T4? ______Why? ______Will the affected individual suffer from hyper- or hypothyroidism?Circle one: hyper- hypo-

Why? ______

  1. Based on Wendy’s lab results, signs, and symptoms, what would your diagnosis be for Wendy? ______Explain your reasoning. ______

______

  1. What special lab test would help you confirm your diagnosis? ______