Lecture 5 - Disorders of the Endocrine System Flashcards
Describe the hypothalamic-pituitary-adrenocortical axis and its regulation.
In response to low blood glucose and stress, the hypothalamus releases CRH (Corticotropin-releasing hormone), which stimulates the anterior pituitary to release ACTH. ACTH then acts on the adrenal cortex to produce cortisol. This axis is regulated by negative feedback.
What are the three sections of the adrenal cortex, and what hormones are produced in each section?
The adrenal cortex is divided into three sections: Zona glomerulosa (produces mineral corticoids like aldosterone), Zona fasciculata (produces glucocorticoids like cortisol), and Zona reticularis (produces adrenal androgens like DHEA).
Name the hormones produced by the adrenal cortex and their functions.
The adrenal cortex produces hormones including cortisol (for fat and protein breakdown and stress resistance), aldosterone (promotes Na+ reabsorption), and DHEA (associated with sex drive in adult females).
Explain the normal functioning of the hypothalamic-pituitary adrenocortical axis using a suppression test and a stimulation test.
In a suppression test with IV dexamethasone, the axis should suppress cortisol production. If it doesn’t, it indicates that cortisol is coming from somewhere other than the axis (e.g., pituitary tumour in Cushing’s Disease). In a stimulation test with synthetic ACTH or an insulin stress test, the axis should produce adrenal glucocorticoids. If the adrenals won’t produce cortisol, it suggests adrenal failure (e.g., Addison’s disease).
What are the potential causes of hypofunction of the adrenal cortex, and how can these conditions be diagnosed?
Causes of adrenal cortex hypofunction include diseases of the gland, secondary adrenal insufficiency, and suppression due to medication. Diagnosis involves assessing high ACTH, low 8am cortisol, and performing stimulation tests (e.g., Synacthen and insulin stress test).
Differentiate between the causes and hormone levels in Cushing’s syndrome and Cushing’s disease.
Cushing’s syndrome results from prolonged exposure to cortisol and can have various causes. Hormone levels are often high. Cushing’s disease is specific to a pituitary adenoma secreting ACTH, which stimulates cortisol production.
Describe the clinical features and diagnostic tests for Cushing’s syndrome.
Clinical features of Cushing’s syndrome include striae (stretchmarks), central obesity, and hypertension. The Dexamethasone suppression test aids in the diagnosis of adrenal hyperfunction.
What is Conn’s syndrome, and how is it diagnosed?
Conn’s syndrome is caused by an adrenal tumor secreting aldosterone. Patients may experience hypokalemia and hypertension. Diagnosis involves blood samples to assess cortisol and aldosterone control.
Explain congenital adrenal hyperplasia (CAH) and its association with 17 and 21 hydroxylase deficiencies.
CAH is caused by deficiencies in 17 or 21 hydroxylase enzymes, leading to issues with steroid biosynthesis and a lack of cortisol. This results in increased ACTH levels due to the absence of negative feedback.
In the context of endocrine disorders, what is the function of DHEA, and how is it regulated?
DHEA, an adrenal androgen, is associated with sex drive in adult females. Its release is regulated by ACTH.
How do you check the normal function of the hypothalamic-pituitary adrenocortical axis, and what do the results indicate?
Checking the normal function of the axis can be done through suppression and stimulation tests. Normal results indicate that the axis is functioning correctly, while abnormal results suggest underlying issues.
What is the significance of the hormone cortisol in the body, and how is its release controlled?
Cortisol plays a role in fat and protein breakdown, stress resistance, and has a circadian rhythm. Its release is controlled by the hypothalamic-pituitary adrenocortical axis.
Describe the typical symptoms associated with adrenocortical insufficiency and the diagnostic tests used to evaluate it.
Symptoms include lethargy, pigmentation of hands and mouth, abdominal pain, weight loss, low blood pressure, and dehydration. Diagnostic tests such as the Synacthen test and the insulin tolerance test are used to evaluate adrenal function.
