Endocrine System & Diabetes Flashcards
- Describe function of the endocrine system.
2. Explain how hormone production is controlled.
The endocrine system regulates metabolic functions and homeostasis via chemical messengers.
Endocrine glands are stimulated to synthesize and release hormones in response to one of three stimuli:
• Hormonal stimuli
• Neural stimuli
• Humoral stimuli
Hormonal stimuli
Hormonal stimuli • Hormones stimulate other endocrine organs to release their hormones – Hypothalamic hormones stimulate release of most anterior pituitary hormones – Anterior pituitary hormones stimulate targets to secrete still more hormones – Hypothalamic–pituitary–target endocrine organ feedback loop • Hormones from final target organs inhibit release of anterior pituitary hormones
Neural stimuli
Neural stimuli • Nerve fibers stimulate hormone release – Example: Sympathetic nervous system fibers stimulate adrenal medulla to secrete catecholamines
Humoral stimuli
Humoral stimuli • Changing blood levels of ions and nutrients directly stimulate secretion of hormones – Example: Ca2+ in blood • Declining blood Ca2+ concentration stimulates parathyroid glands to secrete PTH (parathyroid hormone) • PTH causes Ca2+ concentrations to rise, and stimulus is removed
- Describe how endocrine disorders develop.
Disorders of Endocrine System can result from either hypofunction or hyperfunction of an endocrine gland Primary disorder: originate in target organ releasing the hormone Secondary and tertiary disorder: defect in hypothalamus-pituitary system
- Give examples of different types of endocrine disorders, note their signs and symptoms and identify the different tests and treatment strategies for the disorder.
Disorders of Endocrine Control of Growth & Metabolism
Disorders of the endocrine system most commonly present with signs of either:
1. Hypofunction – due to
– Congenital defects resulting in absence or impaired development of the gland
– Absence of an enzyme needed for hormone production
– Destruction of a gland due to decreased blood flow, infection, autoimmune responses, and neoplastic growth
– Atrophy of the gland due to medication
– Defective receptor sites or the response to the hormone is diminished
2. Hyperfunction – due to
– Excessive hormone production due to over stimulation of the gland
– Hormone producing tumor
Tests used to examine endocrine function
Tests used to examine endocrine function
• Blood – provide information about levels of a
hormone (at the time of the sample)
– Analysed using radioimmunoassay (RIA); ELISA;
autoantibodies; biochemical, etc
• Stimulation – hypofunction
• Suppression – hyperfunction
• Imaging
– Isotopic scanning e.g. the use of radioactive iodine to
assess the ability of the thyroid gland to take up iodine
– Non-isotopic including CT; MRI; PET; ultrasonic scans
Thyroid Hormone (TH)
• Body’s major metabolic hormone - TH affects virtually every cell in body
• Found in two forms (both iodine-containing amine hormones)
– T4 (thyroxine): major form secreted by thyroid follicles (90%); consists of two tyrosine molecules with four bound iodine atoms
– T3 (triiodothyronine): thought to be active form; has two tyrosines with three bound iodine atoms
• Most T3 converted from T4 at tissue level
• TH enters target cell and binds to
intracellular receptors within nucleus
– Triggers transcription of various metabolic genes
Thyroid function tests
• TSH – gives an initial indication of thyroid function • Following an abnormal TSH result – serum FT4 (and FT3) and/or – Thyroid antibodies
• Hyperthyroidism
– Most common cause is Graves’ disease
• Autoimmune disease: body makes abnormal antibodies directed against thyroid follicular cells
• Antibodies mimic TSH, stimulating TH release
– Symptoms include elevated metabolic rate, sweating, rapid and irregular heartbeats, nervousness, and weight loss
despite adequate food
• Exophthalmosmay result: eyes protrude as tissue behind eyes becomes edematous and fibrous
– Treatments include carbimazole tablets (a thionamide) surgical removal of thyroid or radioactive iodine to destroy active thyroid cells
• Primary hypothyroidism
– Common causes
• Autoimmune disease e.g. Hashimoto’s, thyroidectomy, ablation, iodine deficiency
• Subclinical hypothyroidism increases with age and affects more woman than men
– Symptoms include decreased metabolic rate, lethargy, slow pulse, weight gain, cold intolerance, constipation, puffy face, etc
– Treatment is replacement therapy with synthetic preparations e.g. levothyroxine
Insulin
Actions of insulin • INSULIN STIMULATES uptake, use, and storage of glucose – Glucose > glycogen (glycogenesis) – Glucose > fat (lipogenesis) – Protein synthesis • INSULIN INHIBITS – Glycogen breakdown (glycogenolysis) – Fat breakdown (lipolysis) – Protein breakdown > glucose (gluconeogenesis)
Diabetes mellitus
• Diabetes is a disease in which the body’s ability to produce or respond to the hormone insulin is impaired, leading to a state of hyperglycaemia and changes in nutrient
(CHO, PRO & FAT) metabolism and storage
The three Ps
Polyuria - increased urination
Polydipsia - increased thirst
Polyphagia - increases hunger
Type 1 Diabetes
Autoimmune disease - antibodies against beta cells. Often diagnosed in childhood 7-12 Signs and symptoms: Thirst Passing more urine Weight loss Very tired Mood changes
Diagnosed by blood tests treated with insulin.
Type 2 diabetes
The body doesn’t produce enough insulin, or the cells in the body don’t recognise the insulin that is present. The end result is the same: high levels of glucose in your blood.
For many people (but not all) type 2 diabetes can be prevented by making healthy food choices and staying active.
There is a clear link between type 2 diabetes and high blood pressure (hypertension) and / or disordered levels of fats (cholesterol) in the blood (the medical name for this is dyslipidaemia). This combination of diabetes with hypertension and dyslipidaemia is sometimes called ‘the Metabolic Syndrome’ or Syndrome X.
Gestational
Gestational diabetes occurs when a pregnant woman has high levels of glucose in her blood. High blood glucose is caused because the mother can’t produce enough insulin (a pregnant woman’s insulin needs are two to three times that of normal).
A woman who has had gestational diabetes has an increased risk (50-60%) of developing type 2 diabetes in the future; therefore they should be tested for type 2 diabetes each year.
Diabetic ketoacidosis
Diabetic ketoacidosis signs and symptoms often develop quickly, sometimes within 24 hours. For some, these signs and symptoms may be the first indication of having diabetes. You may notice:
Excessive thirst Frequent urination Nausea and vomiting Abdominal pain Weakness or fatigue Shortness of breath Fruity-scented breath Confusion More-specific signs of diabetic ketoacidosis — which can be detected through home blood and urine testing kits — include:
High blood sugar level (hyperglycemia)
High ketone levels in your urine
Diabetes testing
FASTING BLOOD GLUCOSE
= 7mmol/L or greater tells you that you have diabetes.
If your fasting blood glucose level is between 6.1mmol/L and 6.9mmol/L, you may have a condition called “impaired fasting glycaemia” (IFG) or pre-diabetes.
ORAL GLUCOSE TOLERANCE TEST (OGTT)
If you are not pregnant and your blood glucose two hours after an OGTT is 11.1mmol/L or more you have diabetes.
HBA1C LEVEL (ALSO CALLED GLYCOSALATED HAEMAGLOBIN LEVEL)
- No diabetes HBA1c of less than 40mmol/mol
(Target levels for most people with diabetes is 50 - 55 mmol/mol.)
Levels of 65 - 90 mmol/mol indicates your blood glucose levels are much too high
Levels above 90mmol/mol indicates your blood sugars are extremely high
