Thyroid Drugs Flashcards
Name the thyroid hormone drugs
Levothyroxine
Liothyronine
Name the antithyroid drugs
Carbimazole
Propylthiouracil
Describe the pathophysiology of Hypothyroidism
Thyroid hormones are too low to properly regulate physiological function.
Primary: The TSH is high, but T4 is low.
Secondary: The TSH is low and the T4 is low.
Commonly caused by Hashimoto’s disease, where antibodies block TSH receptor on follicle cells -> destroys follicles.
Secondary causes are: Anterior pituitary gland dysfunction and iodine deficiency.
Describe the pathophysiology of Hyperthyroidism
Thyroid hormones are too high to properly regulate physiological problem.
The TSH is low, but T4 is high.
Commonly caused by Grave’s Disease, toxic multinodular goitre and thyroiditis.
What symptoms occur in Hypothyroidism?
- fatigue, memory impairment, depression
- shaggy hair, hair loss
- swelling face, swelling eye socket
- dry rough skin
- slowed heart rate, weakness
- weight gain
- constipation
- diminished fertility, low sex drive, cycle disorder
- muscle cramps
What symptoms occur in Hyperthyroidism?
- nervousness, irritability, insomnia, depression
- broken hair, hair loss
- bulging eyes
- warm, moist skin, increased body temperature
- increased heart rate, arrhythmia, high BP
- weight loss, high appetite
- diarrhea
- cycle disorders
- fragile fingernails, shaking hands
- muscle weakness
What are potential complications of Hypothyroidism?
Myxoedema Coma
What are potential complications of Hyperthyroidism?
- Cardiac problems: cardiac arrhythmias, congestive heart failure
- Osteoporosis
- Thyrotoxicosis crisis
What is the mechanism of action of the antithyroid drugs?
Thioamines:
* Carbimazole: (Prodrug) converts to methimazole and blocks peroxidase catalysed reaction -> blocking iodination of tyrosine residues on thyroglubulin and coupling of DIT and MIT.
* Propylthiouracil: Inhibits thyroid peroxidase and inhibits the peripheral conversion of T4 to T3
Radioactive Iodine Sodium: Taken up by the thyroid gland and damages it
Potassium Iodide solution: provides significant amount of iodine to switch off hormone production from HPT feedback mechanism (used mainly for acute thyroid storm)
Anion inhibitors: blocks uptake of iodide from iodide transporters via competitive inhibition
What is the mechanism of action of the thyroid hormone drugs?
Levothyroxine: Exerts the same physiological effects as T4.
Liothyronine: Exerts the same physiological effects as T3
What occurs in Parathyroid Gland disorders?
Hyperparathyroidism: Too much parathyroid hormone (PTH) leading to excess calcium levels
Hypoparathyroidism: Not enough PTH leading to too low calcium and high phosphorus levels
What is Osteopenia and Osteoporosis?
Osteopenia is the precursor to osteoporosis. Osteoporosis is where osteoclast bone resorption is not compensated with osteoblast bone formation resulting in weak and brittle bones.
What is Osteomalacia?
Bone softening due to a lack of calcification -> mainly caused by vitamin D deficiency.
What is Paget’s Disease?
Excess bone resorption and growth leading to skeletal deformaties and potential fractures
What causes metabolic bone disorders?
Nutrient/mineral deficiencies (calcium, vitamin D, magnesium, phosphorus), hereditary hypophosphatemia and hyperparathyroidism.
