Thyroid Gland: Case Studies

Question 1

Primary hyperthyroidism

Answer 1

-hypothalamus -> Low TRH -> anterior pituitary -> Low TSH -> defect in thyroid -> High T4 and T3

Question 2

Secondary hyperthyroidism

Answer 2

-hypothalamus -> low TRH -> anterior pituitary -> high TSH (defect) -> thyroid -> high T4 and T3

Question 3

TH excess/hyperthyroidism

Answer 3

• patients have elevated BMR tachycardia, sweating, heat intolerance
• nervousness
• muscle wasting and weakness
• tremor
• difficulty sleeping
• changes in hair growth and skin texture
• patients develop toxic goiter- enlarged thyroid containing increased amounts of THs on TG
• most common form is Grave’s disease
• thyroid-stimulating immunoglobulins are present in circulation and cause hypertrophy of thyrocytes, resulting in goiter
• increasing circulating TH leads to decreased TSH release from anterior pituitary by a negative feedback effect however. The stimulatory immunoglobulins continue to stimulate secretion of high amounts of TH by acting directly on TSH receptors in the follicle cells
• some patients also experience exophthalmos and eyelid retraction
• thyroid storm, an exacerbation of hyperthyroidism

Question 4

Clinical Symptoms of Hyperthyroidism

Answer 4

• can increase metabolic rate by 30-60% over normal
• goiter can be caused by both hypothyroid and hyperthyroid conditions and results from TSH, or immunoglobulin-mediated stimulation or hyperplastic growth of the thymocytes

Question 5

Primary hypothyroidism

Answer 5

• hypothalamus
• high TRH ->
• anterior pituitary -> high TSH
• > thyroid -(defect)-> Low T4 and T3

Question 6

Secondary hypothyroidism

Answer 6

-hypothalamus -> high TRH -> anterior pituitary -> defect thyroid -> Low T4 and T3

Question 7

Hypothyroidism diseases-

Answer 7

• the most common form is Hashimoto’s thyroiditis (1% of females), an insidious slow developing process
• Hashimoto’s is an autoimmune disorder with production of antithyroid antibodies, which gradually destroy the gland
• dietary iodine deficiency leads to hypothyroidism and goiter
• there is elevated TSH and reduced TH in patients with primary disease
• myxedema coma is the end stage of untreated hypothyroidism, a medical emergency in hypothyroid patients

Question 8

TH deficiency

Answer 8

• patients have a low BMR, cold intolerance, lethary, increased fat deposition, hypotension, nonpitting edema, headache, skin changes, constipation
• patients can develop, non toxic goiter (enlarged thyroid due to fibrosis and lymphocytic infiltration)
• Hashimoto’s patients have reduced TH, which leads to increased TSH due to reduced negative feedback. However, the thyroid gland cannot response to TSH because it is being destroyed by the antithyroid antibodies
• Hashimoto’s patients are typically treated with thyroxine
• hypothyroid individuals who are iodine deficient are treated with dietary iodine