HYPOTHYROIDSM-THYROID UNDER ACTIVITY
This is the inability of the thyroid to secrete sufficient quantity of hormone needed by the body.This is ranges from mild and clinically unimportant to moderate to severe.When the condition go to extreme it may result in life threatening myxedema coma.
Classifications
Primary 1.This is due to tissue damages or malfunctions of the gland by diseases,or destructive therapies such as over or toxic radiations by radio therapies,and mistaken surgeries.
2.Under development and under maturity of the gland by incompetence or congenial.e.g cretinism
Secondary This is a passive inactivity of the gland by not get enough or nil stimulation by TSH secretion from the pituitary gland.In this the gland is healthy but there may be some problem at the anterior pituitary- gland axis and thereby no secretion of the TSH from the pituitary gland.This may be due to some disease in pituitary gland.
Tertiary In this even if both thyroid and pituitary glands are healthy there may be some problem or defects at the hypothalamus pituitary axis so that there is no hypothalamus secretion of Thyrotropin Releasing Hormone (TRH), to stimulate anterior pituitary to release TSH to stimulate thyroid.
Causes
Hashimoto's thyroditis This is an autoimmune condition in which gland is ineffective as its hormones are inactivated by circulating lymphocyts.This condition is chronic and the gland is damaged by lymphocytes,a kind of WBCs as our body's own immunity.
Toxic treatments of Hyperthyroidsm This may be due to careless and toxic radio iodine treatment of hyperthyroidsm,partial removal of the gland,and over administrations of anti thyroid agents.
Surgical damages
Goiter 1)Endemic goiter this condition develops due to the insufficient or zero intake of dietary iodine supplements.This is common in the region where there are soils devoid of iodine contents.
2)Sporadic goiter This is due to the high intake of foods drugs especially herbal medicines containing a chemical known as Progoitrin which is inactive but will be hydrolysed and converted by our body to the active Goitrin.
Goitrin prevent the oxidation of iodine to iodide and blocking the uptake of iodide by the colloidal thyroglobulin to synthesize the hormone.
Vegetables like cabbage,cauliflower,mustard,spinach,brussels,sprouts,peanuts,horse radish and kale are found to be containing more progoitrin.
Drugs such as Propyl thiouracil,iodide,phenylbutazone,cobalt and lithium are said to be goitrogenic
3.Acute thyroiditis,nodules,nodular goiter and thyroid cancer are also said to contribute hypothyroidsm but to a lesser extend.
Symptoms 1)A the start,signs of lethergy,followed by fatigue,forgetfulness,cold like feelings,weight gain without any proper cause,and difficult tight motion.
2)If not properly attended at the beginning the disease will progress further leads to signs of myxedema will surface such as dry flaky inelastic skin,coarse hair,slowed speech and thought,hoarseness,puffy face,hands and feet.Eyelid loop,hearing loss,menorrhagia,impotence,decreased libido, finally losses all reflexes ends in coma.
TREATMENTS
Treatments are mainly based on replacement therapy by drugs
Desiccated thyroid preparations-Variant ratio preparations
In olden days the desiccated thyroid preparation were considered as drug of choice but slowly they lost its favour as more favourable synthetic safe and fast therapeutic agents such as synthetic levothyroxin preparations are available.
Eventhough the desicated thyroid preparation met the USP creteria they are not bioequivalent as their T-3 and T-4 contents are varying.The contents are variying according to their source of preparations.Porcine gland preparations were having higher T-3 to T-4 variations when compared with the preparations from ovine and bovine sources.
Fixed ratio preparations
These are synthetic preparations in order to minimize the variations of the ratio of T-4/T-3.and they almost mimic the glandular functions.In these preparations T-3 component are almost unnecessary because of its disadvantages like tremor,headache,palpitations and diarrhea.Hence preparations like Levothyroxin (Levothroid,Synthroid,and Levoxyl) contains only T-4 and hence the disadvantages of T-3 are nill.Eventhough these contains only T-4 after consumption the body would convert it to T-3 and get the glandular benefits with minimum side effects.Hence these preparations are the drugs of choice.
The average adult maintenance dose is 75 to 150 mic.gm/day for Levothroid and Synthroid.
The dose range is shown to be 1.5 to 1.7 or an average of 1.6 mic/kg/day.for otherwice healthy patients.
Elderly or longtime ill patients require 50 to 100 mic.gm/day as an average dose.
Thyroxin levels become normal within a few weeks and full recovery may be seen after 3 to 6 months.
Precautions and monitoring effects to the patients
1.Adult patient with a history of heart problems should begin with a low dosage like 25 mic.gm/day and gradually increase the dose after 3 to 4 weeks to 100 mic/gm/day.
2.Patient should be watched for cardiac arrhythmias,palpitations,and anginal pain on initiating the therapy.
3.Serum T-4,RT-3U,and TSH levels should be monitored.FTI should also to be monitored.
4.Sensitive TSH test should be observed 2 to 6 months after the last dosage is recommended .However the test continue to change for 1 year. Testing early may result into over treatment.
5.Long time Levothyroxine may precipitate hyperthyroidsm;even at the recommended constant dosage T-4 level may increase to induce thyrotoxicosis and hence monitor carefully.
6.Patients receiving replacement therapy with low TSH values may have lower bone mineral density since the excess hormone accumulation may have the effect on the bone resorption to the boneformation equillibrium to result in bone fracture.
7.Cholestyramine a bile acid cholesterol reducing drug may lower the bioavailability of thyroxine on co-administration.
Mixedema coma The most serious emergency situation of hypothyroidism claims high mortality rate.
Common in elderly patients and in patients with under estimated diagnoses.
Precipitating factors are alcohol,sedatives and narcotic uses;over use of anti thyroid agents;
Abrupt discontinuation of thyroid hormone therapy.
Infections;
Exposure to extreme cold temperatures;
Toxic radiations;
Thyroid surgery.
Symptoms
The patient will fall from lethargy to coma.
Hypothermia,and a fall in respiration follows.
Decrease in metabolic rate leads to fluid retension
Decrease in sodium level.
Decrease in heart rate.
Treatments include rapid restoration of T-3 and T-4 levels to normal
Desiccated thyroid preparations can be tried with risk.More preferably the synthetic Liothyronine (Cytomel)is reseved for the treatments of Myxedema coma.
A loding dose of 400 to 500 mic.gm is given as an I.V. bolus.followed by a maitenance dose of 25 mic.gm is given orally every 6 hrs.
Treatment should be continued until improvement is noted.Then Levothyronine is discontinued followed by the Levothyroxine with the maitenance dose of 100 mic.gm/day.
Fixed ratio preparations
These are synthetic preparations in order to minimize the variations of the ratio of T-4/T-3.and they almost mimic the glandular functions.In these preparations T-3 component are almost unnecessary because of its disadvantages like tremor,headache,palpitations and diarrhea.Hence preparations like Levothyroxin (Levothroid,Synthroid,and Levoxyl) contains only T-4 and hence the disadvantages of T-3 are nill.Eventhough these contains only T-4 after consumption the body would convert it to T-3 and get the glandular benefits with minimum side effects.Hence these preparations are the drugs of choice.
The average adult maintenance dose is 75 to 150 mic.gm/day for Levothroid and Synthroid.
The dose range is shown to be 1.5 to 1.7 or an average of 1.6 mic/kg/day.for otherwice healthy patients.
Elderly or longtime ill patients require 50 to 100 mic.gm/day as an average dose.
Thyroxin levels become normal within a few weeks and full recovery may be seen after 3 to 6 months.
Precautions and monitoring effects to the patients
1.Adult patient with a history of heart problems should begin with a low dosage like 25 mic.gm/day and gradually increase the dose after 3 to 4 weeks to 100 mic/gm/day.
2.Patient should be watched for cardiac arrhythmias,palpitations,and anginal pain on initiating the therapy.
3.Serum T-4,RT-3U,and TSH levels should be monitored.FTI should also to be monitored.
4.Sensitive TSH test should be observed 2 to 6 months after the last dosage is recommended .However the test continue to change for 1 year. Testing early may result into over treatment.
5.Long time Levothyroxine may precipitate hyperthyroidsm;even at the recommended constant dosage T-4 level may increase to induce thyrotoxicosis and hence monitor carefully.
6.Patients receiving replacement therapy with low TSH values may have lower bone mineral density since the excess hormone accumulation may have the effect on the bone resorption to the boneformation equillibrium to result in bone fracture.
7.Cholestyramine a bile acid cholesterol reducing drug may lower the bioavailability of thyroxine on co-administration.
Mixedema coma The most serious emergency situation of hypothyroidism claims high mortality rate.
Common in elderly patients and in patients with under estimated diagnoses.
Precipitating factors are alcohol,sedatives and narcotic uses;over use of anti thyroid agents;
Abrupt discontinuation of thyroid hormone therapy.
Infections;
Exposure to extreme cold temperatures;
Toxic radiations;
Thyroid surgery.
Symptoms
The patient will fall from lethargy to coma.
Hypothermia,and a fall in respiration follows.
Decrease in metabolic rate leads to fluid retension
Decrease in sodium level.
Decrease in heart rate.
Treatments include rapid restoration of T-3 and T-4 levels to normal
Desiccated thyroid preparations can be tried with risk.More preferably the synthetic Liothyronine (Cytomel)is reseved for the treatments of Myxedema coma.
A loding dose of 400 to 500 mic.gm is given as an I.V. bolus.followed by a maitenance dose of 25 mic.gm is given orally every 6 hrs.
Treatment should be continued until improvement is noted.Then Levothyronine is discontinued followed by the Levothyroxine with the maitenance dose of 100 mic.gm/day.
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