Thyroid Diseases

Question 1

Hypothyroidism and its classification

Answer 1

Hypothyroidism is a disorder of the endocrine system in which the thyroid gland does not produce enough thyroid hormone.
CLASSIFICATION
A. Congenital: can be as a result of
- Maldevelopment of thyroid gland–hypoplasia or aplasia;
- Inborn deficiencies of biosynthesis or action of thyroid hormone;
- Atypical localization of thyroid gland;

B. Acquired:
• Primary (thyroid gland disturbances): can be as a result of a variety of reasons
- Environmental iodine deficiency
- Autoimmune processes (hypothyroidism usually occurring as a sequel to Hashimoto’s thyroiditis)
- Surgical removal, total thyroidectomy of thyroid carcinoma, subtotal thyroidectomy
- Irradiation (hypothyroidism results from external neck irradiation therapy in doses 2000 rads or more such as are used in the treatment of malignant lymphoma and laryngeal carcinoma);
- During or after therapy with propylthyouracil, methimazole, iodides
- Medications such as amiodarone, interferon alpha, thalidomide, lithium, and stavudine have also been associated with primary hypothyroidism.
- Trauma

• Secondary: It occurs due to either deficient secretion of TSH (Thyroid Stimulating Hormone) from the pituitary or lack of secretion of TRH (Thyroid Regulating Hormone) from the hypothalamus. This could be due to;

• Hypothalamic tumors (including craniopharyngiomas)
• Inflammatory (lymphocytic or granulomatous hypophysitis)
• Infiltrative diseases
• Hemorrhagic necrosis (Sheehan’s syndrome)
• Surgical and radiation treatment for pituitary or hypothalamic disease
• Drugs (reserpin, parlodel).
• Tertiary: similar to secondary mostly due to hypothalamic diseases.
• Peripheral: can be because of
• peripheral tissue resistance to thyroid hormones;
• production of antibodies to thyroid hormones.

C. Laboratory (subclinical) hypothyroidism: It is an asymptomatic state in which serum T4 (thyroxine)and free T4 are normal but TSH is elevated .

D. Clinical hypothyroidism where T3, T4 and TSH are decreased which can be divided on stages of severity: mild, moderate, severe.

E. Based on the stages of compensation; subcompensation and decompensation

F. With complications (myopathy, polyneuropathy, encephalopathy, coma) and without complications

Question 2

Clinical features, diagnosis and treatment of hypothyroidism

Answer 2

Clinical features:
•	Weight gain
•	Increased sensitivity to cold
•	Muscle weakness
•	Fatigue
•	Hoarseness of voice
•	Constipation
•	Muscle stiffness
•	Bradycardia, hypotension, decreased cardiac output - cardio
•	Periorbital edema
•	Menorrhagia 
•	Cretinism in children: severe mental retardation, short status, coarse facial features, protruding tongue
•	Myxedema: slow of physical and mental activity, mental sluggishness, overweight, non-pitting edema at hands, feet, eyes

Laboratory diagnostics:
• primary hypothyroidism: decrease in T4(1.1-1.8), T3(0.8-2.0)and increase TSH(0.28-4.0 norm)
• Secondary hypothyroidism: serum T4, T3 will decrease and decrease TSH
• Electrocardiograph: sinus Brady cardia with low voltage complexes’ segment and t wave abnormalities.
• Nonspecific abnormalities:
-serum enzymes: increase creatine kinase, aspartate aminotransferase, lactate dehydrogenases
-hyper cholesterolemia
-anemia: normochromic
-hyponatremia
-mild proteinuria
-GFR decreased
-hyperlipidemia
Thyroperoxidase antibodies TPO( <34 in norm)
TSH receptor autoantibodies (1.75 in norm)
TREATMENT.
Symptoms are easily controlled with synthetic l.-thyroxine. Most patients need 0.15 mg/day. In women the replacement dose is usually lower, and many do well on 0.1 mg/day.
Age<65 with heart conditions- 25-50mg/kg/day
Without- 12.5-25mg/kg/day.
In pregnant women- more than 2mg/kg/day
-Levothyroxine
-Triiodothyronine combination therapy.
-

Question 3

Hyperthyroidism

Answer 3

definition:it’s hyper secretion of thyroxine from thyroid gland that increases body metabolism.
Classification
Primary( grave’s, drugs, adenoma)
Secondary (TSH secreting pituitary adenoma, TRH syndrome, gestational thyrotoxicosis)

Thyrotoxicosis without hyperthyroidism
- subacute thyroiditis, silent thyroiditis.
predisposing factors:
1-Increased synthesis and secretion of the thyroid h. From thyroid ( Graves disease,
multinodular goiter, toxic adenoma)
2-Iodine induced (drugs: amiodarone)
3-TSH-secreting pituitary tumor
4-Struma ovarii
5–Choriocarcinoma, weak thyroid stimulator
6-Fastitious

-degrees of the thyroid enlargement:
Grade 0-Can’t see/ palpate thyroid gland
Grade 1- Palpable, not visible
Grade 2-Palpable and visible

Question 4

Clinics, diagnosis, treatment of hyperthyroidism

Answer 4

Symptoms: weight loss, heat intolerance, Palpitations, Tremor, Irritability, Tachycardia, Palma erythema, Warm, moist, smooth skin, Hand tremor, Muscle weakness, Alopecia, Pruritus, Sweating, Amenorrhea/oligo menorrhea, infertility, gynecomastia.
-graves diseases: opthlmolopath (periorbital edema, diplopia), pretibial myxedema- non pitting infiltrated ground substance.

Lab.diagnosis:
-TSH is decreased with increase T3,T4
-Antithyroid peroxidase(anti-TPO): antibody elevation with autoimmune thyroid disease (graves’ disease.
-TSH receptor antibody(TRab), TSab, TSI is elevated in graves’ disease.
N/B: presence of this anti body support the diagnosis of autoimmune thyroid disease

Imaging:

• radionuclide imaging
• ultrasound-enlarged thyroid gland, hypo echogenic parenchyma
• CT/MRI: for retrosternal extension
• X-ray – replacement of gland
• CBC: normocytic anemia’s
• CMP: hypercalcemia (T3 activates osteoclast)

TREATMENT:
Hyperthyroidism known as GRAVE’S DISEASE.
1) Antithyroid drugs:
- Methimazole
- Propylthiouracil
- Carbinazole
2) Drugs to ameliorate thyroid hormone effects:
- Beta-adrenergic blocking drugs (Propanolol)
3) Iodine therapy: iodine, radioactive iodine 131
4) Surgery: large goiters, <21years
5) Treatment endocrine ophthalmopathy: steroids, electrophoresis, dehydration.