Week 8 - Adrenal Flashcards
What are the roles of the adrenal cortex and the adrenal medulla?
Adrenal cortex = produces steroid hormones
Adrenal medulla = catecholamine secretion
What is the structure of the adrenal gland?
- Capsulated
- 3 layered outer cortex
- Zona glomerulosa
- Zona fasiculata
- Zona reticularis
- Inner medulla
- Secretion under SNS control
Is this a steroid-secreting cell or peptide-secreting cell?
Why?
Steroid-secreting cell
- Has smooth ER
- Has lipid droplets
- Has tubular cristae in mitochondria
Is this a steroid-secreting cell or peptide-secreting cell?
Why?
Peptide-secreting cell
- Has RER and Golgi
- Has granules
- Has normal mitochondria
What is the innervation of the adrenal medulla?
How does it act?
Sympathetic innervation = sympathetic ganglion
- Secretion = controlled by preganglionic neurons
- Quick release
- Act on adrenergic receptors
What are the pathology of adrenal gland?
- Hypoadrenalism
- Addison’s disease
- Hyperadrenalism
- Conn’s syndrome, Cushing’s syndrome, malignant tumour, ectopic syndrome, neuroendocrine lung tumour
- Phaeochromocytoma
- Benign adrenal tumour, neuroectodermal origin
- catecholamine oroductino = hypertension
What are the symptoms and diagnosis of phaechromocytoma?
Symptoms:
- Headaches
- sweating
- Palpitations
Diagnosis = urinary catecholamines or metabolites
What is the rate-limiting step of steroidgenesis?
Transport of cholesterol from outer to inner mitochondrial membrane
What is produced by each of the zona glomerulosa, zona fasciculata, and zona reticularis?
Zona glomerulosa = aldosterone
Zona fasciculata = cortisol
Zone reticularis = androstenedione (testosterone i.e.)
How do the steroid hormones aldosterone and androgens act on target cells?
Aldosterone = act on DCT and Cd, promoting Na+ reabsorption and K+ elimination during urine formation (SECRETION STIMULATED BY + K+ CONC. AND RAA)
Androgens = secretion starts age 5-6, + in women, regulated by ACTH
Require transportation via plasma protein carriers
What are the metbaolic actions of cortisol?
- Stress hormone
- Elevate ACTH levels
- AVP and CRH action
- Affects sleep / wake cycle
- in morning, - in evening
- Catabolic in muscle and adipose
- Stimulate gluconeogenesis and glycogen storage in liver
- Inhibit glucose uptake, + glucose production
- Counter-regulation against insulin
What are the anti-inflammatory/ immunosppressive effects of cortisol?
- Stimulate lipocortin 1 production = no prostanoids or leukotrienes
- number and activation of T-lymphocytes
- cytokine production
- Stabilises lysosomes
- Decrease in NO production
What is the role of cortisol in the stress response?
+ CV tone
+ glucose availability
- energy consuming activities
SNS response
What are the implications of prolonged elevated cortisol levels?
- Muscle wasting
- Hyperglycaemia
- GI ulcers
- Impaired immune response
What is Cushing’s syndrome and what are the primary and secondary causes?
Excessive glucocorticoid activity
Endogenous or exogenouse (Ex = + use of glucocorticoids)
- Primary = adrenal carcinoma or adenoma
- Negative feedback = + cortisol, - ACTH
- Secondary = pituitary or ectopic ACTH-secreting tumour
- Tumour cells have impaired negative feedback response
What are the symptoms of Cushing’s syndrome and causes of each?
- Truncal obesity and red round face (altered fat deposition)
- Female frontal balding, hirsutism, menstrual irregularities (excessive adrenal androgen production)
- Testicular atrophy, thin arms + legs, muscle weakness, thin skin, purple striae (breakdown of protein)
- Poor wound healing, easy bruising, skin infections (collagen loss)
- Cognitive difficulties, emotional instability, depression, sleep distrubance (mental changes)
- Osteoporosis, hypertension, diabetes (altered bone metabolism, insulin resistance)
- Growth retardation in children
How do you diagnose Cushing’s syndrome?
- Cortisol measurements
- plasma cortisol = Cushing’s
- Tests of loss of diurnal cortisol rhythm
- ACTH levels distinguish primary from secondary
- Dynamic tests
- Suppression test
How do you treat Cushing’s disease?
- Localisation of tumour
- Surgery or radiotherapy
- Drugs to inhibit steroidgenesis
