Q1. Which of the following is not true for Hashimoto thyroiditis?
a) It is an autoimmune disease caused by CD4 cells with specificity to thyroid antigens
b) commonly presents as hypothyroidism
c) Surgery is required in almost all cases
d) Hashimoto thyroiditis can progress to lymphoma of thyroid
Q 2. In which of the following conditions anti thyroid antibody may not be elevated?
a) Hashimoto thyroiditis
b) Grave's disease
c) Multinodular goitre
d) Lymphoma thyroid
Answers
1. c
Hashimoto's thyroiditis is an autoimmune process that is thought to be initiated by the activation of CD4+T (helper) lymphocytes with specificity for thyroid antigens. Hypothyroidism is due to cytotoxic cells and autoantibodies.
Primary treatment is Thyroxine and surgery is only indicated for cosmetic reasons .
Hashimoto's thyroiditis more common in women (male: female ratio 1:10 to 20) between the ages of 30 and 50 years.
Commony presents as moderately enlarged firm gland discovered on routine physical examn or the awareness of a painless anterior neck mass, although 20% of patients present with hypothyroidism, and 5% present with hyperthyroidism (hashitoxicosis)
Chances of lymphoma are more in cases with hashimoto's thyroiditis.
2. d
Antibodies include antithyroglobulin (anti-Tg), antimicrosomal or antithyroid peroxidase (anti-TPO) and thyroid-stimulating immunoglobulin (TSI). Anti-Tg and anti-TPO antibody levels they indicate the underlying disorder, usually an autoimmune thyroiditis. Approximately 80% of patients with Hashimoto's thyroiditis have elevated thyroid antibody levels, but levels may also be increased in patients with Graves' disease, multinodular goiter, and, occasionally, with thyroid neoplasms
In Grave's disease antibodies are directed against (TRAbs) (thyroid hormone receptors) (TSI)
Notes
Iodine Metabolism
The average daily iodine requirement is 0.1 mg. Iodine is rapidly converted to iodide in stomach and jejunum. Iodide is actively transported into the thyroid follicles.
Thyroid Hormone Synthesis involves four steps
1.Thyroid trapping of iodide
2. Oxidation of iodide into iodine and coupling with tyrosine to form monoiodotyrosine and diiodotyrosine.
3. Coupling to form T3 and T4
4.Hydrolisation of Thyroglobulin to release T3 and T4
In the euthyroid state, T4 is produced and released entirely by the thyroid gland, whereas only 20% of the total T3 is produced by the thyroid. Most of the T3 is produced by peripheral deiodination of T4 in the liver, muscles, kidney, and anterior pituitary,
The thyroid gland is capable of autoregulation, which allows it to modify its function independent of TSH. As an adaptation to low iodide intake, the gland preferentially synthesizes T3 rather than T4, thereby increasing the efficiency of secreted hormone. In situations of iodine excess, iodide transport, peroxide generation, synthesis, and secretion of thyroid hormones are inhibited.
