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.
The following drugs can lead to iodine excess, EXCEPT:
a. amiodarone
b. aminosalicylic acid
c. aminoglutethimide
d. verapamil.
d. verapamil.
All the other drugs in the choices can lead to drug-induced primary hypothyroidism. Other examples include: interferon-a, cytokines and lithium.
Most common cause of congenital hypothyroidism
a. Thyroid gland dysgenesis
b. Inborn errors of thyroid hormone synthesis
c. TSH-R mediated
d. sarcoidosis
a. Thyroid gland dysgenesis.
Congenital hypothyroidism occurs in 1 in 4,000 newborns. Causes include: Thyroid gland dysgenesis (80-85%), Inborn errors of thyroid hormone synthesis (10-15%) and TSH-R mediated (5%).
All of the following are symptoms of congenital hypothyroidism, EXCEPT:
a. prolonged jaundice
b. enarlged tongue
c. hypotonia
d. overeating
d. overeating.
Signs & Symptoms of Congenital hypothyroidism:
- prolonged jaundice,
- feeding problems,
- hypotonia, 4.enlarged tongue, 5. delayed bone maturation,
- umbilical hernia
True or False: The best way to diagnose hypothyroidism is through lab tests.
True. Pertinent history findings and the signs and symptoms of hypothyroidism are common in many other conditions meaning lab tests are absolutely essential.
Signs & symptoms of hypothyroidism?
1. Cold intolerance 2. Delayed relaxation of deep tendon reflexes 3. Constipation 4. Dry skin 5. Tiredness, weakness, lethargy 6. Myxedematous skin changes (generalized, puffy face, hands and feet) 7. Arthralgia 8. Hoarseness 9. Mental clouding, 10. depression 11. Hair loss, Diffuse alopecia 12. Difficulty concentrating, 13. poor memory 14. Carpal tunnel syndrome 15. Serous cavity effusions 16. bradycardia
The pallor to yellow tinge in hypothyroid patients is due to:
carotene accumulation. (yung bilirubinemia ay sa hyperthyroidism)
True or False: Liothyronine is the treatment of choice for hypothyroidism.
False. It is levothyroxine
Name a cause of thyrotoxicosis without hyperthyroidism.
- Exogenous intake of levothyroxine
- subacute thyroiditis
- thyroid destruction
True or False: Hyperthyroidism is a subset of Thyrotoxicosis.
True. Thyrotoxicosis is the more general term as it is the general state of thyroid hormone excess while hyperthyroidism is excessive thyroid function leading to thyrotoxicosis.
PRIMARY or SECONDARY Hyperthyroidism: Graves’ Disease
PRIMARY
PRIMARY or SECONDARY Hyperthyroidism:
McCune-Albright Syndrome
PRIMARY.
McCune-Albright Syndrome occurs due to the activating mutation of Gsa leading to hyperfunctioning thyroids.
What is the Jod-Basedow Phenomenon?
PRIMARY Hyperthyroidism resulting from excessive iodine intake.
- So basically para siyang opposite ng Wolff-Chaikoff effect since instead na mag-result to hypothyroidism, nagiging hyperthyroid ang patient probably because of thyroid abnormalities na nagcause sa gland magfunction w/o control from the pituitary.
Thyrotoxicosis due to excessive ingestion of thyroid hormone:
Thyrotoxicosis factitia
refers to the short period of thyroid hormone suppression which happens in normal persons and in persons with thyroid disease, when comparatively large quantities of iodine or iodide are ingested.
Wolff-Chaikoff effect
SIGNS & SYMPTOMS of Hyperthyroidism
- Hyperactivity, - irritability,
- Heat intolerance and
sweating - Palpitations
- Fatigue and weakness
- Weight loss despite
increased appetite - Diarrhea
- Polyuria
- Oligomenorrhea, loss of libido
- Tachycardia, atrial fibrillation
- Tremor
- Goiter
- Warm, moist skin
- Muscle weakness, proximal
myopathy - Lid retraction
- Gynecomastia
True or False. Graves’ Disease is the most common cause of thyrotoxicosis.
True. 60-80%
Cause of Graves’ Disease?
- Genetic and environmental factors
o HLA-DR, CTLA-4, PTPN22 (T-cell regulatory gene)
o Increased iodine intake, stress, smoking - Thyroid stimulating immunoglobulins (TRAbs/
TSI); anti-TPO positive in 80%
Consistency of goiter in Graves’ Disease.
Firm.
- 2-3 times normal size, with bruits due to increased vascularity of the glands and onycholysis.
Pathophysiology og Graves’ Ophthalmopathy
Caused by Cytokines and T cell infiltration of the eye, activation of fibroblasts and increased synthesis of glycosaminoglycans
that trap water -> muscle swelling, later with fibrosis of muscles
True or False: Thyroid Storm is a clinical diagnosis and NOT based on lab tests.
True.
Thyroid storm is most commonly precipitated by:
infection
The scoring system used to diagnose Thyroid Storm
Burch-Wartofsky Scoring System
The class of drugs used as first line treatment for hyperthyroidism.
Thionamides
The most severe adverse effect of anti-thyroid drugs:
Agranulocytosis - occurs in <1% of patients
Signs of a positive Pemberton’s sign?
- facial congestion, redness, cyanosis and respiratory distress
- elicited by asking patient to raise both arms which causes intrathoracic goiter to press and block the venous outflow from the head -> cyanosis
- Pemberton’s sign is indicative of Superior Vena Cava Syndrome
There is iodine deficiency if urinary iodine level is less than:
<10ug/dl
Thyroid function abnormality occurs in how many percent of patients with goiter?
8.53%
Most common endocrine malignancy
Thyroid Cancer
Medullary thyroid carcinoma originates from ___ cells
C-cells (calcitonin-producing cells)
Papillary and follicular thyroid carcinomas orginate from _____ cells
thyroid follicular cells
PAPILLARY or FOLLICULAR Thyroid Cancer:
Most common.
PAPILLARY
Deadliest thyroid cancer, such that most patients die within 6 months.
Anaplastic thyroid cancer.
