Conditions of the Endocrine System Flashcards
Describe the condition of hypertcortisolism
Definition:
- umbrella term for a range of conditions characterized by excessive circulating cortisol levels
- Cushing’s disease: caused by increased ACTH secretion from anterior pituitary
- Cushing’s syndrome: occurs independently of ACTH secretion
Aetiology:
- Cushing’s Disease: usually caused by a pituitary microadenoma (benign hormone secreting tumour in anterior pituitary)
- Cushing’s Syndrome: usually iatrogenic (glucocorticoid hormone therapy)
- other: tumour of adrenal cortex, neuroendocrine tumours of the lung (SCLC) that produce ACTH
SSX (caused by increased glucocorticoid activity)
- tunical obesity
- abdo striations
- buffalo hump
- ‘moon face’ with flushed red cheks
- muscle atrophy
- myalgia, arthralgia
- osteoperosis and bone fractures
- insulin resistance
- poor wound healing and skin infections
- if zona reticularis involved, SSX of hyperandrogenism (hirsuitism, menstrual irregularity)
Management:
- if untreated 50% fatality rate within 5 years
- pituitary / adrenal / neuroendocrine tumours: surgery, radio and/or chemotherapy
- iatrogenic: discontinue glucocorticoid therapy
Which types of tumours can cause hypercortisolism?
- pituitary microadenoma
- 70% of cases
- benign hormone secreting tumour of anterior pituitary gland - tumour of adrenal cortex
- neuroendocrine tumours of the lung (SCLC / small cell lung carcinoma)
- secrete hormones including ACTH
Describe the condition of adrenal cortical hypofunction
Definition:
- inability of adrenal cortex to produce sufficient cortical hormones
Classifications:
- Primary adrenocortical insufficiency
- high ACTH levels, decreased cortisol
- called Addison’s disease
- caused by intrinsic dysfunction of adrenal cortex (usually autoimmune attack) - Secondary adrenocortical insufficiency
- low ACTH and cortisol levels
- caused by pituitary or hypothalamic dysfunction or after glucocorticoid therapy
SSX:
- decreased mineralocorticoid activity (dehydration, hypotension, hyperkalaemia)
- decreased glucocorticoid activity (hypoglycaemia, postural hypotension)
- systemic (severe fatigue, weakness, weight loss, GI disturbance)
- skin changes (hyperpigmentation caused by excess ACTH secretion, vitiligo)
Management:
- hormone supplementation (cortisol for glucocorticoids, fludocortisone for mineralcorticoids)
Acute adrenaocortical insufficiency /Addisonial crisis / adrenal crisis:
- medical emergency
- IV fluids and cortisol
- life threatening emergency associated with severe hypotension, hyperkalaemia, hypoglycaemia
What is Addison’s disease?
- another term for primary adrenocortical insufficiency (adrenal cortical hypofunction)
- caused by intrinsic dysfunction of adrenal cortex
- 80% of cases caused by autoimmune attack
- characterized by normal ACTH and low cortisol levels
What is ACTH and how is it implicated in the conditions hypercortisolism and adrenal cortical dysfunction?
ACTH:
- adreno corticotrophic hormone
- produced by anterior pituitary gland
- stimulates release of cortisol and androgens
In hypercortisolism (Cushing’s Disease):
- increased ACTH secretion from anterior pituitary
- causes excessive amounts of circulating cortisol
In primary adrenocortical insufficiency (Addison’s)
- ACTH levels are normal, but cortisol levels are high because of adrenal cortex dysfunction
In secondary adrenocortical insufficiency:
- ACTH levels are low, causing low cortisol levels
- caused by pituitary or hypothalamic dysfunction
What are the symptoms of abnormally high cortisol levels (hypercortisolism) and abnormally low cortisol levels (adrenal cortex hypofunction)
High:
- tunical obesity, moon face, buffalo hump
- muscle atrophy, osteoperosis
- myalgia, arthralgia
- insulin resistance
- HTN
- poor wound healing and skin infections
Low:
- severe fatigue
- weight loss
- GI disturbances
- hyperpigmentation
Describe the condition of phaeochromocytoma
Definition:
- adrenal tumour arising from chromaffin cells of adrenal medulla
Pathophysiology:
- most common cause of excess catecholamine production (epinephrine, norepinephrine)
SSX:
- CVD (HTN, AMI, stroke, AAA, heart failure, palpitations)
- systemic (pallor, sweating, weight loss)
- GI (abdo pain, vomiting, constipation)
- other (severe HA, anxiety, tremours)
Management:
- can cause death by catastrophic hypertensive crisis or fatal cardiac arrythmias
- surgical resection
- long term adrenergic blockade
Which group of hormones is affected by phaeochromocytomas?
Phaeochromocytomas:
- adrenal tumour arising from chromaffin cells
- cause increased catecholamine production (epinephrine, norepinephrine)
Describe the condition of simple / non-toxic goitres
Definition:
- enlarged thyroid gland
- thyroid function maintained
Classifications:
- simple diffuse (uniform enlargement) - most common in young women, pregnant women
- simple multinodular (enlargement with nodule formation)
Aetiology:
- iodine deficiency
- most common cause
- higher levels of TSH are secreted to maintain normal levels of T3 and T4
- causes hyperplasia of follicular cells in thyroid and resulting enlargement - Other:
- ingestion of goitrogens (lithium, tobacco)
- pregnancy, OCP
- early stage Hashimoto’s thyroiditis
SSX:
- simple diffuse
- soft and symmetrical goitre
- neck tightness with swallowing
- non tender
- no bruit - simple multinodular
- can become very large
- if haemorrhaged into a nodule: pain and oedema
- if compressing mediastinal structures: cough, dysphagia, stridor, oedema
Management:
- asymptomatic simple: observation
- iodoine supplementation (helps childhood goiotres, doesn’t impact adulthood goitres)
- if compressive SSX: partial thyroidectomy (high risk of recurrence)
What are dietary sources of iodine, and how is iodine implicated in goitres?
Dietary sources:
- dairy, eggs, seafood
Iodine:
- synthesizes production of T3 and T4 from thyroglobulin in thyroid glands
- if insufficient iodine: T3 and T4 levels drop, so anterior pituitary secretes more TSH (thyroid stimulating hormone)
- elevated TSH causes hyperplasia of follicular cells
Describe the condition of hypothyroidism
Definition:
- deficiency of T3 and T4 thyroid hormones
Classifications:
- Primary:
- caused by thyroid gland failure
- most common cause: Hashimoto’s thyroiditis (autoimmune)
- other causes: iatrogenic, congenital, iodine deficiency - Secondary:
- caused by TSH deficiency
- caused by pituitary adenoma, pituitary surgery - Tertiary:
- caused by TRH deficiency
- caused by hypothalamic dysfunction
SSX:
- puffiness and pallor = sterotypical features
- myxedema (non-pitting oedema) especially in hands, feet and eyelids (periorbital oedema) - caused by GAG / glycosaminoglycan accumulationo in various body tissues
Describe the condition of Hashimoto’s thyroiditis
Definition:
- autoimmune disease of thyroid gland causing hypothyroidism
Incidence:
- most common type of primary hypothyroidism in Aus
- 10 x more common in females
- typically onset in middle age
Precipitating factors:
- high iodine supplementation
- lithium amiodarone drugs
Pathophysiology:
- autoimmune disorder
- lymphocyte mediated inflammation and fibrosis of thyroid
- secretion of IgG antibodies against thyroglobulin and thyroid peroxidase
- causes goitre (early stage)
- causes thyroid atrophy (late stage)
Describe the condition of thyrotoxicosis
Definition:
- clinical state caused by an excess of thyroid hormones
Classifications:
- toxic diffuse goitre (Grave’s)
- toxic multinodular goitre
- toxic solitary nodule
Aetiology:
- usually caused by hyperthyroidism
- can also be caused by levothyroxine ingestion
SSX:
- goitre
- diffuse enlargement
- audible bruit - ocular changes (GAG accumulation)
- lid retraction and bulging eyes
- corneal ulceration and conjunctivitis
- excessive lacrimation
- diplopia
- decreased visual acuity - increased metabolic rate
- heat intolerance
- weight loss
- sweating - GIT
- increased appetite and thirst
- hyperdefecation, diarrhea - CVS / Respiratory
- palpitations and atrial fibrillation
- exacerbated asthma - neuro
- nervousness, emotional lability, psychosis
- hyper-reflexia, tremor
- muscle atrophy - reproductive
- menstrual irregularities
- loss of libido - skin
- GAG accumulation in skin of legs causes pretibial skin myxedema and thicke
Management:
- anti-thyroid drugs, beta-blockers, radioactive iodine
- surgery: sub-total thyroidectomy (risk for hypothyroidism, damage to laryngeal nerves or parathyroid gland)
- good prognosis with management, risk for hypothyroidism
Describe Grave’s disease
Definition:
- toxic diffuse goitre
- autoimmune disease
- most common cause of thyrotoxicosis (excess of thyroid hormones)
Incidence:
- 8 x more common in females
Risk factors:
- familyl history, high dose iodine supplementation, major stressors causing an autoimmune response
Pathophysiology:
- autoantibodies present in 50% of cases are directed against thyroid stimulating hormone receptors
- causes goitre production and elevated T3 and T4 levels
Describe the condition of thyroid cancer
Incidence:
- 7th most common cancer in women
- much more common in women
Risk factors:
- family history
- benign thyroid disease
- exposure to ionizing radiation (20 years latency)
Classifications:
- papillary carcinoma (80%, begins as a solitary nodule and spreads through gland)
- follicular, medullary and anaplastic carcinomas
SSX:
- rapid onset nodule enlargement (firm and non-tender)
- large tumours can cause discomfort, dysphagia, Horner’s syndrome
- metastatic spread: Cx lymphadenopathy
Management:
- excellent prognosis: if tumour under 2cm, patient under 50 and no spread, no change to life expectancy
- surgical resection
- hemi or total thyroidectomy
