Thyroid, parathyroid

Question 1

Thyroid hormone function

Answer 1

• Act on nearly every cell in the body
• Regulates metabolism
• Increase glucose metabolism
• Increase protein synthesis
• Increase oxygen consumption (blood pressure, heart rate)
• Reegulates growth and tissue differentiation
• Digestion
• Reproduction
• Bone growth
• Muscle tone
• Development of nerve cells

Question 2

Hyperthyroidism

Answer 2

• Diffuse hyperplasia of the thyroid
• Hyperfunctional multinodular goitre
• Caused by impaired synthesis of thyroid hormone, often from iodine deficiency, leads to compensatory TSH increase, causing hypertrophy and hyperplasia of thyroid follicular cells

Question 3

Graves disease

Answer 3

A cause of hypertrophy which is an autoimmune disease characterised by production of thyroid protein autoantibodies, and against the TSH receptor which MIMIC TSH action- trick the receptor into thinking there’s TSH there, so we create more T3 and T4

Question 4

Diagnosis of hyperthyroidism

Answer 4

Measure serum TSH concentration, typically it will be low. Confirmed by measuring T4 which will be high

Question 5

Treatment of hyperthhyroidism

Answer 5

Radioactive iodine- higher concentration of iodine in the thyroid, the radioactivity will damage the follicular cells

Question 6

Hypothyroidism and causes

Answer 6

Under-active thyroid gland, usually caused by genetic defects in thyroid development, thyroid hormone resistance, surgery, radioiodine therapy, autoimmunity, iodine deficiency, drugs (eg lithium), biosynthetic defect, pituitary or hypothalamic failure (rare)

Question 7

Cretinism

Answer 7

Hypothyroidism in infancy or early childhood- impaired development of the skeletal system and central nervous system- severe mental retardation, short stature, coarse facial features, protruding tongue and umbilical hernia

Question 8

Myxedema

Answer 8

Hypothyroidism in older children or adults- fatigue, shortness of breath, mental sluggishness due to reduced cardiac output (may mimic depression), slowing of physical and mental activity, frequently overweight, decreased sympathetic activity-constipation and decreased sweating- skin is coll and pale due to decreased blood flow.

Question 9

Thhyroiditis

Answer 9

Inflammation of the thyroid gland- encompasses a diverse group of disorders characterised b inflammation, massive immune cell infiltration and leading to extensive fibrosis in the long term.

Question 10

Hashimoto thyroiditis

Answer 10

Painless enlargement of the thyroid, low T4 and T3, sometimes preceded by high levels.
CD8+ T Cell mediated cell death- apoptosis, destruction of follicular cells

Question 11

Subacute lymphocytic (painless) thyroiditis

Answer 11

• Middle aged adults- more commonly women

- Similar to Hashimoto-autoimmune- clinically and histologically.

Question 12

Granulomaous thyoiditis

Answer 12

In contrast to autoimmune thyroid disease, the immune response is virus-initiated and not self perpetuating, the process in limited- histologically distinct, we have multinucleated “Giant Cells” (they try for cell division but are unable to divide the cytoplasm

Question 13

Latrogenic hypothyroidism

Answer 13

Caused by a medical procedure:
-Large resection of the gland (total thyroidectomy) for treatment of hyperthyroidism or a primary neoplasm.
-Radiation, whether in the form of radio-iodine administered for the treatment of hyperthyroidism, or exogenous irradiation, such as external radiation therapy to the neck
Drugs given to decrease thyroid secretion can also cause acquired hypothyroidism, including agents used to treat non-thyroid conditions (eg lithium)

Question 14

Parathyroid gland

Answer 14

• Regulate calcium homeostasis

- Controlled by level of free calcium in the bloodstream, decreasedd levels stimulate the sythesis nd secretion of PTH

Question 15

Hyperparathyroidism

Answer 15

• One of the most common endocrine disorders, important cause of hypercalcaemia
• Commonly caused by a sporadic solitary parathyroid adenoma, a pericentromeric inversion of chromosome 11 causing over-expression of cyclin D1- uncontrolled cell division

Question 16

Hypoparathyroidism: causes

Answer 16

• Its rare
• Surgically-induced hypoparathyroidism occurs with inadvertent removal of all the parathyroid glands during thyroidectomy, excision of the parathyroid glands (mistaken belief that they are lymph nodes, during radical neck dissection for a malignant disease)
• Autoimmune hypoparathyroidism may accompany a long-term infection
• Extremely rare genetic conditions or congenital absence of parathyroid glands can occur in conjunction with other malformations

Question 17

Hypoparathyroidism symptoms

Answer 17

• Tetany, characterised b neuromuscular irritability, decreased serum calcium levels
• Mental status changes
• Intra-cranial manifestations included calcifications of the basal ganglia, parkinsons-like movement disorders, increased intra-cranial pressure
• Ocular disease takes the form of calcification of the lens and cataract formation
• Cardiovascular manifestations-conduction defect on ECG
• Dental hypoplasia, failure of eruption, defective enamel and root formation, and abraded carious teeth due to hypocalcaemia

Question 18

Treatment of hyperparathyroidism

Answer 18

Calcimimetics- drugs that mimic calcium circulating in the blood, thereby inhibiting parathyroid hormone release

Question 19

Treatment of hypoparathyroidism

Answer 19

Supplements including vitamin D and calcium