Endocrinology Flashcards
What are hormones?
Molecules secreted by endocrine glands into the blood with regulatory actions at distant sites
What are the two types of receptors that endocrine glands act via?
Cell surface eg insulin
Intracellular eg thyroxine, steroid hormones
Hormones are regulated by __________ ______
Feedback loop
List all the endocrine glands. (6 points)
- Pituitary gland
- Thyroid and parathyroid glands
- Adrenal glands (medulla and cortex)
- Pancreas (islets of Langerhans)
- Ovaries
- Testes
Hypothalamus: CRH (corticotropin-releasing hormone)
Pituitary: ACTH (adrenocorticotropic hormone)
Target organ: _______
Product: ________
Adrenal cortex
Cortisol
Hypothalamus: TRH (thyrotropin-releasing hormone)
Pituitary: TSH (thyroid stimulating hormone)
Target organ: _______
Product: ________
Thyroid
Thyroxine
Hypothalamus: GHRH (growth-hormone-releasing hormone)
Pituitary: GH
Target organ: _______
Product: ________
Liver
Insulin-like growth factor-1 (IGF-1)
Hypothalamus: GnRH (gonadotropin-releasing hormone)
Pituitary: LH (luteinising hormone), FSH (follicle-stimulating hormone)
Target organ: _______
Product: ________
Gonads
Testosterone, Oestrogen, Gametogenesis
What are the hormones produced from non-pituitary axes? (What are their control systems?)
Adrenaline (CNS)
PTH (Plasma calcium)
Aldosterone (Plasma volume via kidneys - renin and angiotensin)
Insulin & glucagon (Plasma glucose)
What are the mechanisms of endocrine disease?
Destruction of gland - autoimmune, cancer, surgery, tuberculosis
Stimulation of gland - autoimmune, tumour formation causing hypersecretion of hormone, mechanical pressure effects from tumour
Tuberculosis destroys adrenal gland
What is the endocrine syndrome where the adernal cortex produces too much cortisol?
Cushing’s Syndrome
What are the possible causes of Cushing’s syndrome?
Exogenous steroids
ACTH-secreting pituitary tumour
Cortisol-secreting adrenal adenoma or carconima
Exogenous = prescribed to suppress inflammation
- Moon face
- Buffalo hump
- Abdominal obesity
- Proximal muscle weakness
- Abdominal striae – stretch marks
- Thin skin
- Bruising
- Osteoporosis
- Hirsutism (androgenic) = females grow man like hair
- Hypertension
- Oedema
- Raises blood glucose level (GH/ adrenaline/ glucagon)
These clinical features are indicative of ___________ syndrome
Cushing’s
How to investigate Cushing’s syndrome?
Raised urine or serum cortisol (measured over 24 hours)
Fails to suppress cortisol production with dexamethasone
ACTH level (pituitary driven cushings = high ACTH; adrenal driven cushings eg adrenal tumour = low/normal ACTH)
Imaging of pituitary/adrenals
Treatment of Cushing’s syndrome usually surgical eg ___________ or _________
Adrenalectomy (removal of adrenal gland or tumour)
Hypophysectomy (removal of pituitary gland or tumour)
What is the name of the hypo-adrenalism disease?
Addison’s disease
What are the possible causes of Addison’s disease?
- Autoimmune destruction of adrenal cortex
- Suppression of HPA axis following steroid therapy
- Adrenal metastases
- TB
- Surgical removal of tumours/glands
- Pituitary failure (ACTH lack)
HPA = hypothalamic-pituitary-adrenal
- Tiredness
- Weight loss
- Pigmentation in skin, palmar creases, buccal
- Hypotension
- Hypoglycaemia
What could these clinical features indicate?
Hypoadrenalism
Why do people with hypoadrenalism get pigmentation?
ACTH is made in the pituitary from a precursor hormone (pro-opiomelanocortin) which also cleaves into melanocyte-stimulating hormone (MSH) which stimulates the pigment cells in the skin. Increased MSH alongside increased ACTH due to feedback loop.
What are the clinical features of Addisonian Crisis?
Vomiting
Dehydration
Hypotension
Hypoglycaemia
Electrolyte disturbances
Investigation of hypoadrenalism:
Low cortisol levels
High ACTH (High if due to primary adrenal failure; low if due to pituitary failure)
Adrenal antibodies
Imaging of adrenals
What is the treatment for hypoadrenalism?
Hydrocortisone (pharmaceutical name for cortisol)
Fludrocortisone (synthetic mineralcorticoid equivalent of aldosterone)
Increase (double the dosage) of hydrocortisone to cover/help illness or stress
Intravenous fluids/electrolytes/glucose and hydrocortisone for Addisonian Crisis
What hormones are in excess in hyperthyroidism?
Thyroxine (T4)
Tri-iodothyronine (T3)
What are the possible causes of hyperthyroidism?
Graves disease (autoimmune stimulation)
Multinodular goitre
Thyroid adenoma
TSH excess (very rarely)
Features of hyperthyroidism (sped up metabolism):
- Feels hot
- Sweaty palms
- Weight loss
- Increased appetite
- Poor sleep
- Loose bowels
- Tremor
- Tachycardia/atrial fibrillation
- Goitre
- Graves eyes (exophthalmos, lid retraction/lag, eye movement restriction)
How to diagnose hyperthyroidism?
Blood test: raised T4 and T3; suppressed TSH; thyroid stimulating antibodies (cause Grave’s disease so check if it’s Grave’s disease level)
Thyroid imaging and isotope scans
How to treat hyperthyroidism?
Radioactive iodine (most common and effective)
Surgical thyroidectomy
Anti-thyroid drugs (only temporary)
Beta-blockers for symptom control
What is hypothyroidism sometimes called (old-fashioned term)?
Myxoedema
Infiltration of interstitial tissues with proteinaceous fluid
What are the hormone levels like in hypothyroidism?
Lack of T4 and T3
High TSH
What are possible causes of hypothyroidism?
Autoimmune destruction of thyroid
Surgical removal of thyroid
Radio-iodine treatment (can easily destory too much cells in the thyroid gland)
Secondary to TSH lack in pituitary disease
What are the clinical features of hypothyroidism?
Opposite of hyperthyroidism
- Feels cold (may get hypothermia)
- Dry skin, thin hair
- Slow, tired, confused
- Slow pulse
- Weight gain
- Poor appetite
- Sluggish bowels
Myxoedema - Coarse facial features
- Bags under eyes
- Croaky voice
Diagnosis of hypothyroidism based on blood test results:
Low T4 and T3
High TSH
Thyroid autoantibodies
How to treat hypothyroidism?
Thyroxine tablets
What hormone is in excess in acromegaly?
Growth hormone
What causes acromegaly?
Pituitary tumour secreting GH
When suspected, what investigations can be carried out to diagnose acromegaly?
Measure GH and IGF-1 in the blood
High GH level (that does not get suppressed by high glucose given, which it normally would)
Raised IGF-1
Pituitary MRI (to check for presence of tumours)
Visual field testing (important for all pituitary tumours)
- Enlarged hands, feet, jaw (malocclusion), skull (change in hat, shoes, dentures, rings sizes)
- Coarse facial features - nose, brow, tongue
- Thick skin
- Arthritis including TMJ
What are these clinical features of?
Acromegaly
What are the metabolic features of a patient with acromegaly?
Hypertension
Hyperglycaemia (due to insulin resistance)
Headache due to pituitary tumour
Bitemporal hemianopia due to the compression of optic chiasm by the pituitary tumour
What is hyperparathyroidism caused by?
Parathyroid adenoma, sometimes hyperfunction of all 4 glands, rarely carcinoma
What does hyperparathyroidism cause?
Hypercalcaemia
What causes hypercalcaemia?
Hyperparathyroidism
Vitamin D excess
Cancers
What are the clinical features of hypercalcaemia?
- Often asymptomatic or non-specific
- Kidney stones (stones), bone pain (bones), ingestion due to excressive production of gastric acid OR constipation OR bowel colic (abdominal groans) and psychic moans
- Dry eyes and mouth
- Thirst and polyuria, due to inability to concentrate urine
How to diagnose hyperparathyroidism OR hypercalcaemia caused by hyperparathyroidism?
Blood test: high plasma calcium with raise PTH
Imaging of parathyroids
If hypercalcaemia not caused by hyperparathyroidism (caused by other factors), what will be shown in the blood test result?
Low PTH
Treatment of hyperparathyroidism usually involves ________ ________ of parathyroid glands.
Surgical removal
What does hypoparathyroidism cause?
Hypocalcaemia
What can cause hypoparathyroidism?
Autoimmune destruction
Damage to parathyroids during thyroid surgery
What are the clinical features of hypocalcaemia?
- Tingling (a sensation)
- Paraesthesiae (tingling/prickling/burning sensation caused by pressure on or damage to peripheral nerves)
- Cramps (involuntary muscle contraction)
- Tetany (abnormal serum electrolyte concentration causing overstimulation of peripheral nerves and can cause muscle cramps)
How to diagnose hypocalcaemia caused by hypoparathyroidism?
Low plasma calcium
Low PTH
How to differentiate hypocalcaemia caused by other causes (eg vitamin D deficiency) from hypocalcaemia caused by hypoparathyroidism?
High PTH in other causes of hypocalcaemia
How to treat hypocalcaemia?
Vitamin D analogues (less urgent situation; high doses needed)
Calcium injection (emergency)
PTH for replacement is not available
