WEEK 5 - Endocrine Disorders Flashcards
What is the endocrine system?
Consists of groups of cells (glands) that make hormones and release them directly into the bloodstream (ductless)
Principles of hormones?
- They are chemical messengers
- They control the activity of the cells they bind to
- Hormones will only bind to cells that have their receptors on their surface
What are the principal endocrine glands?
Hypothalamus Pineal Pituitary Parathyroid Thyroid Thymus Adrenal (cortex and medulla) Pancreas (islets of Langerhan) Ovaries (female) Testes (male)
Functions of the endocrine system?
- Maintain homeostasis
- Control reproduction
- Promote smooth, sequential growth and development
- Regulate RBC production
- Digestion and absorption
- Stress response - fight or flight
What is the hypothalamic-pituitary axis?
The control of the hypothalamus over the release of hormones of the anterior and posterior pituitary glands
How does the hypothalamus communicate with the anterior pituitary?
Via a vascular pathway, the anterior pituitary releases its hormones straight into the bloodstream when stimulated via hormones of the hypothalamus
How does the hypothalamus communicate with the posterior pituitary?
Via a neural pathway, neurosecretory cells connect the two glands, have their cell bodies in the hypothalamus and secrete hormones when stimulated via APs
What hormones does the anterior pituitary secrete?
- Growth hormones
- Gonadotrophic hormones
- Adrenocorticotrophic hormones
Trophic - regulate the secretion of hormones of another gland
What hormones does the posterior pituitary secrete?
Vasopressin and oxytocin
How does the endocrine system regulate homeostasis?
Via negative feedback systems
Principles of endocrine dysfunction?
- HYPOsecretion - not enough hormone, may be due a problem with the gland (primary) or with the hormone itself (secondary)
- HYPERsecretion - too much hormone, may be due to tumours (primary) or with the hormone itself (secondary)
- Target cell hyporesponsiveness - decreased number of receptors or impaired function, does not allow the target cell to respond adequately to hormones (eg. insulin resistance)
What is syndrome of antidiuretic hormone secretion?
High levels of ADH despite normal circulating blood volume and serum osmolality - causes fluid acculumation
Syndrome of antidiuretic hormone secretion is caused by?
- Cancers
- Trauma
- Infection of the CNS
- Drugs
Clinical manifestations of syndrome of antidiuretic hormone secretion?
Serum hyposomolarity and hyponatraemia (Na<135mmol/L) Thirst Nausea Fatigue Headache Vomiting Lethargy Dyspnea Seizures, loss of consciousness (cerebral oedema), respiratory arrest (Na+<115mmol/L)
Treatment of syndrome of antidiuretic hormone secretion?
- Correction of underlying problem
- Emergency correction of severe hyponatraemia - GIVE SALT SLOWLY, otherwise can cause seizures and cerebral oedema, rise in ICP
- Diuretics to aid fluid removal
- Fluid restriction and daily weighs
What are the two types of diabetes insipidus and their causes?
Neurogenic:
Caused by insufficient amounts of ADH despite low plasma volumes and high serum osmolality
Nephrogenic:
Caused by an inadequate response by the renal collecting tubules to ADH
Neurogenic diabetes insipidus is caused by?
- Brain tumours
- Neurosurgery
- Increased ICP
- CNS infections
Nephrogenic diabetes insipidus is caused by?
- Genetic abnormalities
- Disorders and drugs that damage renal tubules
Clinical manifestations of diabetes insipidus?
- Serum osmolarity
- Polyuria
- Nocturia
- Extreme thirst and polydipsia
- Hypovolaemia/hypotension
- Poor skin turgor, dry mucous membranes
- Confusion, irritability
Treatment of diabetes insipidus?
- ADH replacement with desmopression aceteate/vasopression
- Fluids - oral or IV
What is hyperthyroidism?
Increased levels of T3 and T4 (thyroid hormones)
What is primary hyperthyroidism and what is it caused by?
Primary = excess thyroid hormone made and secreted by the thyroid gland.
Caused by Graves disease, goiters, follicular adenoma, thyroid medications in excess
What is secondary hyperthyroidism and what is it caused by?
Excessive thyroid stimulating hormone production (TSH)
Caused by TSH-secreting pituitary adenomas
Describe the pathophysiology of graves disease?
Autoimmune disease
T cells stimulate B cells to produce IgG ABs specific to TSH receptors
ABs bind to TSH receptors in the thyroid = stimulate synthesis and secretion of thyroid hormone
