Case Study 1
Mechanisms of Endocrine Control
Leda is a 38-year-old woman who began to experience weight gain, mood swings, and weakness. When her periods became irregular, she went to her physician. Leda’s physician heard the symptoms Leda was concerned about and then ordered a 24-hour free cortisol urine test and an overnight dexamethasone suppression test and measured her serum ACTH levels. The results indicated that Leda had Cushing disease, a condition caused by the hypersecretion of ACTH by the anterior pituitary and resulting in elevated cortisol levels. To confirm the diagnosis, Leda’s physician ordered a cranial MRI to identify the presence of a pituitary tumor.
- The dexamethasone test involves the administration of a synthetic glucocorticoid ( i.e., cortisol). Knowing what you do about negative feedback mechanisms, how might this test be used to assess pituitary function?
- Describe how the steroid hormones, like cortisol, are metabolized in the body. What are the advantages of using a 24-hour urine test to measure this hormone?
- Protein-based and steroid-based hormones trigger cellular responses in different ways. What are the differences between the mechanism of action of ACTH and cortisol on target cells?
Case Study 2
Disorders of Endocrine Control of Growth and Metabolism
Bertha is a 71-year-old woman who takes daily medication for Hashimoto thyroiditis. Last winter, she developed pneumonia. While she did her best to run errands for her husband, she got tired easily and needed to rest frequently. One day, after shoveling the snow outside, her husband came inside to find Bertha lying on the sofa covered in blankets. Her face appeared puffy and her eyelids hung. When he spoke to her, Bertha’s voice was hoarse and her words did not make sense to him. Her respirations were also shallow and slow. Suspecting low thyroid hormone levels were causing the signs, her husband called for an ambulance.
- When testing for hypothyroidism, why is the free T4 level an important measurement? What would the TSH and T4 test results indicate in someone with primary hypothyroidism?
- Using your knowledge of the function of thyroid hormone in the body, explain why Bertha’s respiratory rate was decreased? Why might pleural effusion be present in someone with hypothyroidism?
- What factors in Bertha’s history leave her susceptible to myxedematous coma? What are the physiological aspects involved in myxedematous coma?
Case Study 3
Diabetes Mellitus and the Metabolic Syndrome
Juan is a 44-year-old who works in a warehouse. He is 5′8″, weighs 185 pounds, and has a waist circumference of 41″. At his last visit to the health clinic, Juan’s blood pressure was 140/60 mm Hg. Shortly after having a series of blood tests, his physician called him in to talk about the results. Juan had a fasting plasma glucose level of 107 mg/dL, an HDL level of 37 mg/dL, and a serum triglyceride level of 210 mg/dL.
- What condition is Juan likely presenting with? What are the spectrum of physiological abnormalities that occur with this disorder?
- What is the significance of Juan’s waist diameter? How is truncal obesity hypothesized to increase insulin resistance in the body?
- In type 1 diabetes, there are hypoinsulinemia and hyperglycemia. In type 2 diabetes, it is common to see hyperinsulinemia and hyperglycemia. Why do the differences exist?