CH 251, Respiratory Drugs, Skeletal Muscle Relaxants, Antihypertensive Drugs, Angina Pectoris, Cardiac Arrhythmias, Congestive Heart Failure, Coagulation Disorders and Hyperlipidia, Endocrine Pharmacology, Male and Female Hormones, Thyroid and Parathyroid, Diabetes

Final Exam Objectives

THYROID AND PARATHYROID DRUGS

 Thyroid controls metabolism and works synergistically with growth hormones

Parathyroid controls calcium homeostasis. 

THYROID

Produces two hormones: thyroxine (T4) and triiodothyronine (T3)

Both hormones require tyrosine and iodine as precursors.

Thyroid hormones are controlled by the hypothalamic pituitary gland which secretes thyroid stimulating hormone (TSH).  Increase in T3 and T4 production provides a negative feedback for TSH.

Physiological effects

1. Thermogensis: increases basal metabolic rate (BMR) and therefore heat in the body.

2. Growth and development: stimulates production of growth hormone and directly affects the skeletal development.

3. Cardiovascular: increases heart rate

4. Metabolic effect: increases glucose absorption and lipolysis.

Mechanism of action:

Binds to receptors in cells and induces transcription in DNA.

 Thyroid Disorders:

Hypothyroidism: caused primarily by genetic deficiency.  Secondary causes can be pituitary or hypothalamic deficiency.  Leads to cretinism in children and myxedema in adults.

Hyperthyroidism: caused by excessive pituitary stimulation can lead to Graves disease (thyroid carcinoma).

 Hyperthyroidism

There can be excessive TSH secretion or enlarged thyroid (goiter)

Symptoms:  weight loss, nervousness, insomnia, muscle wasting, increased appetite etc.

Therapy:

Hypothyroidism

PARATHYROID

Parathyroid controls calcium homeostasis.  Calcium is important in muscle contraction, bone mineralization, synaptic transmissions etc.

 P arathyroid Hormone (PTH)

A polypeptide secreted by parathyroid gland which monitors calcium ion balance in the blood.  Balance can be triggered in the kidneys, GI track and bones.

Increased levels of PTH leads to:

1. breakdown of skeletal tissue

2. increase in renal absorption of calcium ions

3. increase in GI absorption of calcium ions

4. PTH increases Vit D conversion to calcitriol which enhances calcium absorption

Bone Homeostasis

Bones provide two functions: rigid framework and calcium source (both contradictory)

The above two functions are balanced as follows:

1. parathyroid hormone: maintains calcium ion balance

2. vitamin D: steroidal chemical obtained from diet or synthesis in the body with the help of UV light and cholesterol. Vit D increases calcium ion and phosphate absorption in GI track and renal system.  Overall influence is to increase bone formation.

3. Calcitonin: antagonist of PTH hence stimulate bone formation.  PTH is the dominant hormone.

4. Other hormones: glucocorticoids and prostaglandins have catabolic effect on bones. However androgens, growth hormone and insulin increase bone formation.

Pharmacological Control

Calcium blood should be about 9.4 mg% blood.  Convulsions can result at 6mg level and sluggishness can result at 12 mg levels of calcium.

Chronic calcium problems may lead to bone calcification which may lead to hypo or hypercalcemia.

Common treatments

Concerns in Rehabilitation:

1. Be aware of symptoms
2. Avoid exercises that will stress the bones and cardiac system.
3. Watch for BP.
4. Monitor heart with ECG for cardiac arrhythmias.

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