The thyroid gland produces thyroid hormones that regulate metabolism. Hypothyroidism occurs when hormone levels are too low, causing slowed functions, while hyperthyroidism is when levels are too high, speeding functions up. Thyroid disorders are treated by replacing hormones (levothyroxine) or inhibiting hormone production/release (propylthiouracil, methimazole, iodide). Precautions must be taken with medications due to potential side effects on heart, liver and other organs.

1. Thyroid gland

2.  The thyroid is a
bilobed gland which
lies anterior and
inferior to the
larynx.
Thyroid gland location

3.  The main functional unit of the thyroid is the
follicle that consist of a single layer of epithelial cells
surrounding a lumen filled with thyroglobulin, which
is the storage form of thyroid hormone.
 The two major thyroid hormones are
triiodothyronine (T3) and thyroxine (T4)
 Iodine is very important in the synthesis of thyroid
hormones

4.  TSH which is
released from the
pituitary gland in
response to TRH
from the
hypothalamus
regulates the
synthesis of thyroid
hormones.
Regulation of thyroid hormones release

5.  Thyroid hormones:
Euthyroidism: normal thyroid function(normal T3,
T4 and TSH level).
Hypothyroidism: inadequate secretion of thyroid
hormones (low T3 and T4 and high TSH), results
in: Bradycardia, poor resistance to cold, and mental
and physical slowing
◦ In children, this can cause mental retardation and
dwarfism
Hyperthyroidism: an excess of thyroid hormones
secretion(high T3 and T4 and low TSH) causing:
Tachycardia and cardiac arrhythmias, body wasting,
nervousness, tremor, and excess heat production.

6.  Thyroid hormones function:
1. General metabolic effects: Increase oxygen
consumption, metabolic rate, heat production
(thermogenesis)
it increases BMR (Basal Metabolic Rate): The
amount of energy (in the form of calories) that the
body needs to function while resting for 24 hours.
2. Increase glucose utilization and oxidation by
muscles, increase hepatic gluconeogenesis.
3. CNS: Influence growth and development, axon
proliferation, myelin sheath formation.
4. CVS: Increase cardiac output and heart rate,
decrease peripheral resistance.
5. G.I. tract and kidneys: Important for function,
increases intestinal motility.

7.  Treatment of
hypothyroidism:
Hypothyroidism usually results from autoimmune
destruction of the gland or the peroxidase
Diagnosed by elevated TSH
Condition presented at birth: Cretinism: Impaired
mental and skeletal development
Condition presented at adulthood: Myxedema:
Muscle weakness, decreased appetite, fatigue, and
lethargy

8.  Is a synthetic thyroid hormone which
is identical to the natural thyroid
hormone thyroxine T4 . The human
organism does not differentiate
between natural T4 and synthetic b/c
of their identical effects. Is converted
to tri-iodo-thyronine T3 in the
peripheral organs and develops its
specific effect at the T3-receptor.
Levothyroxine (T4):

9. Levothyroxine (T4):
 Trade names:
Eltroxin tab : 500 mcg , 100 mcg
Euthyrox tab : 50 Mg , 100 Mg
Therapeutic group: thyroid hormone
 Hormone replacement therapy to treat
hypothyroidism .It is also used to treat or
prevent goiter.

10. Do not use these medicines if :
1. You suffer from hyperthyroidism, myocardial
infarction or myocarditis
2. Drug allergies
3. You suffer from uncontrolled hypoadrenalism or
hypopituitarism

11. Special cautions:
 You suffer from diabetes (insulin or oral diabetes
medication doses may need to be changed
when you start taking levothyroxine)
 You are elderly
 If you have problems with your pituitary gland
 If you suffer from epileptic seizures as they may
occur more frequently.
 You suffer from heart disease, coronary artery
disease, or a history of blood clots
 anemia (lack of red blood cells);
 osteoporosis, or low bone mineral density;
 if you have recently had a heart attack, or are
having any symptoms of a heart attack (chest
pain or heavy feeling, pain spreading to the jaw
or shoulder, nausea, sweating, general ill

12. Levothyroxine is not expected to harm an unborn
baby. If you become pregnant while taking this
medicine, do not stop taking the medicine without
your doctor's advice. Having low thyroid hormone
levels during pregnancy could harm both mother
and baby. Your dose needs may be different during
pregnancy.
 Levothyroxine can pass into breast milk, but it is
not expected to be harmful to a nursing baby.
Do not use this medication without telling your
doctor if you are breast-feeding a baby.
 Changing from one levothyroxine sodium to
another should be done only with personal
medical consultation and with close surveillance
of the patient .

13. How should you take levothyroxine?
 Do not exceed the recommended dose, (once daily)
 Do not share this medication with another person,
even if they have the same symptoms you have.
 Levothyroxine works best if you take it on an empty
stomach, at least 30 minutes before breakfast(once
daily) and try to take the medicine at the same time
each day.
 Do not chew halve or crush the tablet
 Take the medicine with a full glass of water
 Tell your doctor if you consume soybean products
walnuts, and high-fiber foods as they may reduce
the absorption of levothyroxine and the dose may be
changed as a result
 Discontinuation should be done gradually
 If you miss a dose, take it as soon as possible(never
double it)

14. While using levothyroxine, you may need
frequent medical tests.
Tell any doctor or dentist who treats you that you
are using levothyroxine.
Store at room temperature away from moisture
and heat.
It may take several weeks before your body
starts to respond to levothyroxine. Keep using this
medicine even if you feel well.
 Unexplained weight loss may occur while using
this medicine so do not use it for this purpose

15. What should you avoid?
avoid taking the following drugs within 4 hours
before or 4 hours after you take levothyroxine:
Calcium carbonate
Cholestyramine
Ferrous sulfate iron supplement;
Sucralfate;
Sodium polystyrene sulfonate
Antacids that contain aluminum or magnesium

16. Levothyroxine side effects:
1. Fast or irregular heart rate
2. Fever, hot flashes, sweating
3. Sleep problems (insomnia)
4. Changes in your menstrual periods
5. Vomiting, diarrhea, appetite changes, weight
changes
6. Nervousness heart palpitations tachycardia and
intolerance to heat

17. Treatment of hyperthyroidism:
 Excessive amounts of thyroid hormones in the
circulation are associated with a number of
disease states, including Graves disease, toxic
adenoma, and goiter
 TSH levels are reduced due to negative
feedback
 Treatment options:
1. Removing part or all of the thyroid gland
2. Inhibiting synthesis of the hormones
3. Blocking release of the hormones from the
follicle

18. hormones:
• The thioamides: propylthiouracil (PTU, Propyl-
Thiocil® 50mg ) and methimazole
(Mercaptizol® 20mg)
• Therapeutic group : Antithyroid
• MOA: Inhibit the oxidative processes required
for iodination of tyrosyl groups and the
condensation of iodotyrosines to form T3 and T4
, PTU can also block the conversion of T4 to T3
• Have no effect on the thyroglobulin already
stored in the gland; clinical effects of these drugs
may be delayed until thyroglobulin stores are
depleted

20. PTU
• Do not use if you are sensitive to any of its
components
• Consult your doctor if :
1. if you are pregnant, planning to become
pregnant, or are breast-feeding as it may harm
the baby
2. if you have allergies to medicines, foods, or
other substances
3. if you have a history of blood or bone marrow
problems, liver problems, kidney problems, or
lung or breathing problems

21. How to use propylthiouracil:
• Take propylthiouracil by mouth with or without
food.
• Unless directed otherwise by your doctor,
space your doses evenly throughout the day.
• If you miss a dose of propylthiouracil, take it as
soon as possible. If it is almost time for your
next dose, take the 2 doses together, then go
back to your regular dosing schedule
• Some MEDICINES MAY INTERACT with
propylthiouracil. Such as:
Anticoagulants (eg, warfarin), beta-blockers (eg,
propranolol), digoxin, or theophylline because the
risk of their side effects may be increased by
propylthiouracil

22. Cautions:
• Do not drive as it may cause drowsiness or
dizziness
• Propylthiouracil should not be used in
CHILDREN younger than 6 years old

23. Mercoptizol
 Active.I : methimazole
Theu. Group : imidazole derivative
contaning sulfer.
20mg – 30 TAB
can be halved , don’t chew
contraindication : liver problem

24. PTU and Methimazole side
effects:
• Relatively rare adverse effects include
agranulocytosis, rash, edema, GI side effect,
dizziness and drowsiness
• PTU can cause liver toxicity or liver failure and
should be reserved for patients who are
intolerant of methimazole

25. Blocking release of the hormones from the
follicle(Iodide):
• MOA: Iodide inhibits the release of thyroid
hormones from thyroglobulin by unknown
mechanisms
• Iodide is rarely used as the sole therapy and it
is not useful for long-term therapy, because
thyroid ceases to respond to the drug after a
few weeks
• A pharmacologic dose of iodide inhibits the
iodination of tyrosines “acute Wolff-Chaikoff
effect” but this effect lasts only a few days
• Used for potentially fatal thyrotoxic crisis
(thyroid storm) or prior to surgery

26. • Iodide is administered orally
• Adverse effects ◦ Sore mouth and throat ◦
Swelling of the tongue or larynx ◦ Rashes ◦
Ulcerations of mucous membranes ◦ Metallic
taste in the mouth