Endocrinology Flashcards
What is a hormone?
A specific messenger molecule synthesised and secreted by a group of specialised cells called an endocrine gland
What are the 3 classes of hormones?
Steroid hormones - lipids made from cholesterol e.g. sex hormones
Amino acid derivatives - derived from amino acids, especially Tyrosine e.g. adrenaline
Peptide/protein hormones - most common one e.g. insulin
What hormones are released by the Posterior Pituitary?
ADH
Oxytocin
They are made in hypothalamus but secreted by the Post. Pit.
What hormones are released by the Anterior Pituitary?
Thyroid Stimulating Hormone (TSH) Follicle Stimulating Hormone (FSH) Luteinising Hormone (LH) Prolaction (PRL) Growth Hormone (GH) Adrenocorticotrophic Hormone (ACTH)
The pineal gland secretes __________, it promotes sleep. The levels of this hormone are dependent on exposure to _______
Melatonin, exposure to light
What is SAD?
Seasonal Affective Disorder is when too much melatonin is produced. Most common type is Winter Depression
What are the symptoms of SAD?
Fatigue Appetite change (crave sweets or starchy food) Weight gain Irritability Difficulty Concentrating
Exposure to light for several hours of the day is a treatment for SAD because light ________ melatonin production
Inhibits
The Pituitary gland, aka __________, sits in a small bony cavity at the base of the brain called the __________
Hypophysis, called the Sella Turcica
What are some examples of Pituitary Hypofunction?
Pituitary Dwarfism (Lack of GH as kid) Panhypopituitarism (Ant.Pit. doesn't secrete any hormones, screws other glands) Diabetes Insipidus (Failure to secrete ADH)
What are some examples of Pituitary Hyperfunction?
Gigantism (Too much GH in childhood) and Acromegaly (Too much GH in adults)
Hyperprolactinaemia (Over production of prolactin)
What are the Clinical features of Acromegaly?
Enlarged hands and feet Thickened skin Enlargement of Skull and Jaw Enlargement of lips, nose and tongue Glucose intolerance Hypertension
What causes Acromegaly?
A benign pituitary tumour, but anything that can cause the overproduction of GH can be a cause
How is Acromegaly diagnosed?
An oral Glucose tolerance test, If GH levels are above 2mU L then patient has acromegaly
How is Acromegaly Treated?
Bromocriptine is a dopamine agonist that lowers GH levels in 75% of patients
Removal of Tumour if possible
Radiotherapy to destroy an endocrine producing tumour
What is Hyperprolactinaemia?
Elevated levels of plasma prolactin that causes the discharge of milk or a milk-like secretion. Most common in women ages 20-35
What causes Hyperprolatinaemia?
A common pituitary tumour called an Prolatinoma, The bigger the tumour the higher the prolactin levels
Pregnancy
Hypothyroidism
Liver or Renal Failure
Medications like contraceptives, antipsychotics and antidepressents
What are some tests for Hyperprolactinaemia?
Prolactin level test
Renal function test
TSH Levels
MRI to detect possible tumour
What are some treatments for Hyperprolactinaemia?
Bromocriptine and Cabergoline inhibit prolactin synthesis
Surgery to remove tumours
Radiation therapy
The thymus consists of ____ lateral lobes connected by the ________
2 lateral lobes connected by the isthmus
In the thymus follicular cells produce _____ and _____. The parafollicular cells produce _______
T3 (triiodothyronine) and T4 (Thyroxine)
Calcitonin
Calcitonin acts to regulate____________________
Blood calcium levels
T3 and T4 control the rate of ________________. T4 is 10 times _____ potent than T3 but secreted ______.
Metabolic processes
T4 is 10 times less potent than T3 but secreted more
The 4 parathyroid glands produce _________________ which regulates calcium homeostasis
Parathyroid Hormone (PTH)
What are the signs and symptoms of Hyperthyroidism?
Palpitations Weight loss despite normal or increased appetite Fatigue and muscle weakness Tremors Increased Sweating Heat Intolerance Wide/Swollen/Red eyes Goiter
What causes Hyperthyroidism?
Graves’ disease is most common cause (60-80% of cases)
Toxic Multi-nodular Goiter
Treatments involving Thyroid Hormones and Iodine
Thyroiditis
Tumours
What is Graves’ Disease
It is an autoimmune disease caused by an antibody active against the TSH receptor that stimulates the excess secretion of thyroid hormones
How can we diagnose Hyperthyroidism?
TSH levels test
T3 and T4 level tests
Radionuclide uptake (distinguishes between causes, Graves’ will have high uptake, thyroiditis will have low upstake)
What is the likely diagnosis?
TSH levels: High
T4 levels: High
T3 levels: -
Secondary Hyperthyroidism, possible pituitary problem
What is the likely diagnosis?
TSH levels: Low
T4 levels: High
T3 levels: -
Primary Hyperthyroidism
What is the likely diagnosis?
TSH levels: Low
T4 levels: Normal
T3 levels: High
T3 Toxicosis
What is the likely diagnosis?
TSH levels: Low
T4 levels: Normal
T3 levels: Normal
Sub-clinical hyperthyroidism
How do we treat Hyperthyroidism?
Treatment depends on the cause
Goal is to treat with fewest side effects and low incidence of of Hypothyroidism
Antithyroid drugs, radioactive iodoine and surgery are main options for persistent hyperthyroidism
The 2 antithyroid drugs are _________ and ________
Methimazole (Tapazole) and Propylthiouracil (PTU)
Propylthiouracil is used in pregnant patients because________________________________________
Methimazole has been linked to rare congenital abnormalities
What causes Hypothyroidism?
Thyroiditis Removal of Thyroid Iodine deficiency Drug Therapy Pituitary issues
What are the signs/symptoms of Hypothyroidism?
Decreased sweating Dry and coarse skin Lethargy Cold skin Thick Tongue Facial Edema
How do we manage Hypothyroidism?
Hormone Replacement Therapy
Monitor Thyroid Function
What causes Hyperparathyroidism?
Usually resultant from a hormone secreting parathyroid tumour
What are the signs of Hyperparathyroidism?
High blood calcium
Calcium in urine
How do we treat Hyperparathyroidism?
Saline rehydration followed furosemide diuresis, calcitonin and bisphosphonates
Removal of Parathyroids or Tumour
What causes Hypoparathyroidism?
Removal of Parathyroids during thyroid surgery
Autoimmune diseases
Mg deficiency
What are the signs of Hypoparathyroidism?
Low blood Ca levels
Tremors
Tetany
How do we treat Hypoparathyroidism?
High Ca diet
Vitamin D
The adrenal cortex secretes:
Glucocorticoids
Mineralocorticoids
Sex Hormones
Glucocorticoids are secreted in response to _________ which is secreted by the ________ pituitary. The major glucocorticoid is _________
Adrenocorticotrophic Hormone
Anterior Pituitary
Cortisol
What are the 3 main actions of Glucocorticoids?
- Raise blood glucose by decreasing use by non-essential tissues and promote fat breakdown and use for energy
- Inhibit protein synthesis and promote the conversion of proteins to glucose in the liver
- Suppress inflammation reaction
What are the functions Mineralocorticoids?
- Balance water and electrolytes by promoting Na and water resorption
- Promote K excretion
- Increase Blood Volume
The major mineralocorticoid is _________. It is secreted in response to a reduction in _________ and _________. It acts to increase Na and Water resorption.
Aldosterone
Renal blood pressure and flow
The adrenal medulla produces ____________ which stimulate the _________ nervous system. i.e. Adrenaline, Noradrenaline
Catacholamines
Stimulate the sympathetic NS
Cushing’s Diseases is a caused by ____function of the adrenal _______. ______ levels of cortisol give rise to it.
Hyperfunction, adrenal cortex
Excess levels of cortisol
What are the signs and symptoms of Cushing’s Disease:
Weight gain Headache Thirst Muscle Weakness Lethargy/depression Abdominal pain Hypertension Osteoporosis
Cushing’s disease can be ACTH dependent or ACTH independent. Explain the differences
ACTH dependent cases are caused by over production of ACTH by a pituitary tumour
ACTH independent cases are caused by adrenal adenomas or carcinomas
To diagnose Cushing’s disease a ____________ test is performed. If cortisol levels are ______ a day then they have Cushing’s disease.
24 hour urine test
300ug/day
After cushing’s disease is confirmed, ACTH levels are measure at ___, at this time ACTH levels are usually ____. If ACTH levels are greater than ____ per mL then it is ACTH __________. If ACTH levels are less than ___ per mL then it is ACTH __________.
4pm, levels usually low
10pg per mL, Dependent
5pg per mL, Independent
What are the principle treatments for Cushing’s disease?
Reduce the overdose of glucocorticoids
Inhibit glucocorticoid synthesis
Surgery to remove tumours
Addison’s disease is a condition caused by _________ production of ______ steroids
Insufficient
Adrenal
What causes Addison’s disease?
Destruction of the adrenal cortex
Usually Autoimmune but can be due to infection, surgery, neoplasia, haemorrhage and trauma
_______ to the adrenal cortex bring about destruction of the adrenal glands
Antibodies
There are 3 Adrenal Cortex Antibodies(ACAs) what are they?
- Antibodies to steroid 21 hydroxylase (21-OH) which is the most common and specific one
- Antibodies to steroid 17 hydroxylase (17-OH)
- Antibodies to cytochrome P-450, They are not specific because they are found in other tissues
Children have a ____ risk of developing Addison’s disease compared to adults. When they express ____ they have a __% chance of developing Addison’s.
High
ACAs
30
Destruction of the adrenal cortex results in __________ of the feedback inhibition of the _________ and ________
Interruption
Hypothalamus and Ant. Pit.
To diagnose Addsion’s disease ______ electrolyte levels are measured. __________ is most common (90% of patients) finding because aldosterone levels are low. _________ is found in 60-70% of patients.
Serum electrolytes
Hyponatremia
Hyperkalemia
Serum cortisol levels are at their highest between ___ and ___
6am and 8am
What are some tests for Addison’s disease?
The corticotropin (Cortrosyn) stimulation tes
Insulin tolerance test
Metyrapone test
What are the main treatments for Addison’s disease?
Replacement of Mineralocorticoids and Glucocorticoids
What are some medicines used to restore corticosteroid levels?
Cortone
Cortef
Florinef
Dexone
How do we ascertain the level of mineralocorticoid replacement needed?
Monitoring electrolyte levels
Evaluating clinical findings like dizziness and weight gain
