Lec 02: Thyroid Disorders (Adult) - Goiters and Nodules Flashcards
Normal weight of the thyroid gland?
12-20g
Dimensions of a normal thyroid gland? (lengthxbreadthxthickness)
4cm x 1-2 cm x 2-4cm
‘thyroid’ came from the Greek word ‘thyreos’ which means:
shield
Thyroid hormone synthesis begins at how many weeks of gestation?
11 weeks
What is the protein precursor of the thyroid hormone?
Thyroglobulin (Tg)
True or False: The apex of follicular cells surrounding the colloid material in the thyroid gland faces the follicular lumen.
True.
Follicular cells are polarized in such a way that:
- The basolateral surface is apposed to the bloodstream
- The apex faces the follicular lumen
True or False: T4 and T3 act on cell membrane surface receptors.
False. T3 and T4 act on NUCLEAR RECEPTORS to exert effects on thermogenic and metabolic homeostasis.
True or False: serum TSH is the most useful physiologic marker of thyroid hormone action
True.
True or False: T3 is secreted in larger amounts compared to T4.
False. T4 is secreted at concentrations 20-fold higher than T3.
True or False: The TSH from the Hypothalamus stimulates the pituitary to release TRH, which in turn stimulates thyroid hormone synthesis.
False. The hypothalamus secretes TRH to stimulate pituitary release of TSH which stimulates thyroid hormone synthesis.
Thyroid hormones are bound to the following proteins, EXCEPT:
a. thyroid binding globulin (TBG)
b. transthyretin (TTR)
c. albumin
d. NOTA
d. NOTA
* thyroid hormones bound to proteins are inactive.
True or False: 100% of T4 comes directly from the thyroid.
True. On the other hand, only 20% of T3 comes directly from the thyroid. 80% comes from peripherally converted T4
True or False: A greater fraction of T3 is in free form compared to T4.
True. This makes T3 more metabolically potent and active compared to T4.
Most common cause of hypothyroidism?
Autoimmune.
Primary or Secondary Hypothyroidism? Hashimoto’s thyroiditis.
Primary: Hypothyroidism resulting from thyroid gland pathology.
Primary or Secondary Hypothyroidism?
Lack of pituitary TSH.
Secondary. Pag di directly sa thyroid ang underlying cause, secondary na yun.
Primary or Secondary Hypothyroidism?
Sheehan’s syndrome
Secondary. Nasa pituitary gland ang underlying cause of hypothyroidism.
Mean age of diagnosis of hypothyroidism?
60 y/o
Polymorphisms in these two genes increases susceptibility to autoimmune hypothyroidism
HLA-DR and CTLA-4
- Useful markers for autoimmune hypothyroidisms: Antibodies to Tg, TPO, TSH-R
- Examples of autoimmune hypothyroidism include: Hashimoto’s thyroiditis and atrophic thyroiditis.
A condition characterized by mental and growth retardation resulting from lack of treatment of thyroid deficiency in early life.
Cretinism.
*Patients are described as “Christ-like” because they are severely retarded, they can commit no sin.
Eating this food aggravates goiter and cretinism.
Cassava.
Cassava contains thiocyanates which inhibit uptake and transport of iodide by the thyroid gland. This effect however can be corrected by increased iodine intake.