The Thyroid (Part 3)-Hypothyroidism, Myxedema, Cretinism

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HYPOTHYROIDISM

PRIMARY HYPOTHYROIDISM

Primary hypothyroidism is due to diseases of thyroid gland. It is seen in:

1. Autoimmune hypothyroidism (e.g. Hashimoto’s thyroiditis), thyroidectomy and radiation therapy
2. Drugs – lithium, antithyroid drugs & para-aminosalicylic acid
3. Congenital hypothyroidism is seen in iodine deficiency, absent or ectopic thyroid gland, dyshormonogenesis & in TSH receptor mutation.

SECONDARY HYPOTHYROIDISM

Secondary hypothyroidism is due to diseases of Pituitary or Hypothalamus.

Hypopituitarism is caused by:

1. Tumors
2. Pituitary surgery or irradiation
3. Infiltration
4. Sheehan’s syndrome and
5. Isolated TSH deficiency

Hypothalamic diseases causing secondary hypothyroidism are:

1. Tumors
2. Trauma and
3. Infiltration.

The measurement of TSH level and TRH test will help to differentiate these two different types

MYXEDEMA (Hypothyroidism)

Most common cause is primary thyroid disease, often seen in autoimmune thyroiditis, leading to myxedema in adults.

Women are more affected than males.

Symptoms are:

1. Lethargy
2. Tolerance to heat
3. Cold intolerance
4. Slow heart rate
5. Weight gain
6. Dry coarse skin
7. Slow responses and
8. Sluggishness

CRETINISM (Hypothyroidism)

• In children hypothyroidism produces mental and physical retardation, known as cretinism.
• The TBG may be elevated due to maternal hyperestrogenism (total T4 & T3 may be normal).
• The lack of feedback will give elevated TSH level also.
• Maternal hypothyroidism may also cause congenital hypothyroidism in the newborn

EUTHYROID GOITER

• Iodine deficiency may lead to euthyroid goiter.
• There is raised TSH level
• Continued stimulation of gland leads to hyperplasia and goiter.
• Hormone levels are seen in the lower limits of the normal values.

CONGENITAL HYPOTHYROIDISM

in this condition Thyroid hormones are very low or completely absent from birth.

Symptoms include:

• Puffy face,
• Dullness,
• Thick protruding tongue, which get worsened with time. Infants may have choking episodes,
• Constipation,
• Dry brittle hair,
• Jaundice,
• Floppiness,
• Sluggishness and
• Sleepiness

Treatment consists of oral administration of thyroid hormone, which is simple and cheap.

NON THYROIDAL ILLNESS

• T3,T4 and TSH are found to be lowered in acutely ill patients.

LAB FINDINGS IN HYPOTHYROIDISM