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
Hyperfunction of the thyroid gland leads to?
- Excessive thyroid hormone
- Decreased TSH and TRH
- High levels of T3 and 4
Clinical manifestations of hyperthyroidism?
- Bulging eyes
- Goitre
- Weight loss and diarrhoea
- Increased appetite
- Tachycardia and palpitations
- Sweating, flushing
- Hair loss
- Menstrual changes/fertility issues
- Lability and insomnia
- Dsypnoea
Treatment of hyperthyroidism?
- Antithyroid drugs
- Beta blockers for symptoms
- Radioactive iodine ablation
- Thyroidectomy
Define hypothyroidism
Deficient production of thyroid hormone by the thyroid gland, more common in women than in men
What are the causes of hypothyroidism?
- Failure of the thyroid gland to produce thyroid hormone (primary); caused by iodine deficiency, Hashimoto’s disease, loss of thyroid tissue
- Deficiency of TRH/TSH/both (secondary); caused by pituitary or hypothalamic failure, failure to stimulate thyroid function
Pathophysiology of primary hypothyroidism?
- Loss of functional thyroid tissue
- Decreased production of thyroid hormone
- Lack of negative feedback to T3/4 = increase in TRH and TSH secretion
- Leads to low levels of TH and high levels of TRH and TSH
- TSH = goitre
Pathophysiology of seconday hypothyroidism?
- Injury to the pituitary gland = decreased TSH
- Leads to low levels of Th and TSH and elevated TRH
Or
- Injury to the hypothalamus
- Decreased production of TRH
- Leads to low levels of TH, TSH and TRH = thyroid shrinks
Clinical manifestations of hypothyroidism?
- Lethargy/fatigue
- Weight gain and fluid retention
- Normal or small thyroid
- Goitre
- Bradycardia
- Breathlessness
- Cold intolerance
- Constipation
- Muscle pain and weakness
- Depression
- Thinning of hair
- Low libido/decreased fertility
What is Cushing’s disease?
Excessive levels of cortisol secretion of excessive anterior pituitary secretion adrenocorticotrophic hormone (ACTH)
Causes of Cushing’s disease?
Pituitary adenoma
Ectopic ACTH secreting tumours
What is the pathophysiology of Cushing’s disease?
- Pituitary adenoma secretes ACTH
- Increased secretion of ACTH results in increased production of cortisol by adrenal cortex
- Some normal feedback inhibition by cortisol
- Hypercortisolism
Clinical manifestations of Cushing’s disease?
- Weight gain
- High BGLs or diabetes
- Acne
- Increased body and facial hair
- Facial flushing
- Purple striae
- Easy bruising
- Thin extremities
- Osteoporosis
- HTN
- Increased susceptibility to infections
- Irritability and depression
Treatment of Cushing’s diseases?
- Surgery
- Radiotherapy
- Bilateral adrenalectomy
- Medications
What is Addison’s disease?
Primary adrenal insufficiency, adrenal glands fail to produce sufficient cortisol
What is the pathophysiology of Addison’s disease?
- Destruction of the adrenal complex by autoantibodies
- Decreased levels of cortisol
- Increased levels of adrenocoticotrophic hormone due to loss of negative feedback
Clinical manifestations of Addison’s disease?
- Weakness and fatigue
- Anorexia
- Weight loss
- Nausea
- Diarrhea
- Hypoglycaemia
- Hyponatraemia, hyperkalaemia
- Orthostatic hypotension
- Hyperpigmentation
- Addisonian crisis = severe hypotension and vascular collapse as a result of combined effects of hypocortisolism, hypoaldosteronism, extracellular volume depletion and some precipitating stressor
Treatment of Addison’s disease?
- Lifetime daily glucocorticoid replacement therapy e.g. fludrocortisone, hydrocortisone, prednisolone
- Additional cortisol
