Thyroid and Parathyroid Pathology Flashcards
Identify the most common types of presentation of thyroid pathology.
Goitre, and lump
How may goitres feel like upon palpation ? What does this tell us about its nature ?
Smooth, regular = hormonal drive
Acutely inflamed = viral infection
Lumpy = possibly NOT goitre but lump
Distinguish between toxic and non toxic in the context of thyroid pathology.
Toxic = excess thyroid hormones present, and clinical sequella
Non-toxic = clinically non-visible
Identify the main types of euthyroid goitre, and state the main causes of each type.
- Diffuse: in younger people, may be physiological (part of growing up)
- Mutlinodular: in older people, palpable in the neck, can be associated with multiple cysts and hemorrhage but NON NEOPLASIC, simple response of follicular cells abhorrently to signaling
Identify the main causes of hypothyroid goitre.
1) Iodine deficiency (no feedback from thyroid hormones to TSH and TRH, so raised levels of TSH cause proliferation of tissue
e.g. may be due to iodine deficiency in diet, or blocked metabolic pathway
OR
Iodine excess- iodine required for functioning of thyroid follicular cells and sythesis of mature thyroglobulins. If excess, inhibition of peroxidase enzymes and process of iodination, so iodine does not get incorporated into tyrosines
OR
Excess thiocyanate or perchlorate- Inhibit iodine trapping mechanism so no iodine taken up
-These all result in decreased thyroid hormone production, decreased levels in the blood, feedback to the hypoT-pituitary is lost, so increased levels of TRH and TSH, and high levels of TSH binds to receptor on thyroid gland and increase protein synthesis in follicular cells, resulting in hypertrophy of the thyroid. Cells can make more thyroglobulin, but cannot iodinate it.
2) Goitrogens
-Drugs: lithium
-Diet: cabbage, turnips
Lithium may interfere with signaling and feedback, so can cause goitre and hypothyroidism
Cabbage may interfere with thyroid hormone processing in thyroid causing TSH response
3) Genetic
4) Reactive (post-infectious, e.g. following mumps infection)
Describe possible histological findings of iodine induced goitre.
Cystic glands, areas with more proliferated follicles
Distinguish between benign and malignant masses in the thyroid region.
- Benign masses are usually movable, soft, and non tender.
- Malignancy is associated with a hard nodule, fixation to surrounding tissue, and regional lymphadenopathy (enlarged local lymph nodes.
Identify the main symptoms of solitary thyroid nodules (benign or malignant)
• Most patients asymptomatic, but some exhibit signs and symptoms of altered levels of thyroid hormones:
- Hyperthyroidism
- Hypothyroidism (especially if the solitary nodule is actually nodular part of goitrous gland)
• Signs and symptoms of local nerve involvement (may be indicative or local invasiveness from malignancy) including dysphagia and hoarseness
Identify the main signs and symptoms of hypoT. What presents an obstacle for diagnosis ?
Indolent onset
Cold intolerance, constipation, fatigue, and weight gain (which in children, is primarily caused by the accumulation of myxedematous fluid), thickening of skin, slow speech, deep hoarse voice, lethargy, bradycardia, mental impairment.
Many populations, especially in cold, deprived areas, may demonstrate many of these symptoms without being hypOT.
Identify the main signs and symptoms of hyperT.
Nervousness, heat intolerance, increase in skin temperature and sweating, diarrohea, loss of weight and appetite
(possible exophthalmos in Grave’s), tremor, tachycardia, high metabolic rate, muscle weakness
• Two common manifestataons are diffuse toxic goitre or toxic nodular goitre.
What are other differential diagnoses for what may appear to be a solitary thyroid nodule ?
A larger nodule which is part of a goitrous thyroid
Describe cytology findings of thyroid malignancy.
May be different sized follicles BUT may look benign even in malignancy
Fine needle aspiration can be useful if follicles look normal
Describe the epidemiology of solitary thyroid nodules.
Mainly in younger people (especially physiological, benign nodules)
Females affected more than males
Describe diagnosis of solitary thyroid nodules.
TESTS
- Thyroid function tests - An elevated thyroid-stimulating hormone (TSH) level may indicate thyroiditis; a very low TSH level indicates an autonomous or hyperfunctioning nodule (but in many situations, asymptomatic and no change in thyroid hormones produced). Blood T3 and T4 may also be measured.
- Antithyroid antibodies - Helpful in diagnosing chronic lymphocytic thyroiditis (Hashimoto thyroiditis)
- Complete blood count (CBC) –Abscess (with a goitre)
- Fine needle aspirate (can help distinguish between benign and malignancy)
- Molecular studies (can help determine if particular mutation is present, but diff mutations exist)
IMAGING STUDIES -Ultrasonography • Radionucleotide thyroid scan (123I- or 99mTcO4 -uptake) viewed by a gamma camera -Chest radiography -CT/MRI
What is the use of ultrasonography in the diagnosis of solitary thyroid nodules ?
To determine whether the nodule is cystic, solid, or mixed
What is the use of radioiodine scintigraphy in the diagnosis of solitary thyroid nodules ?
To determine whether the nodule is cold, warm, or hot.
What is the use of chest radiography in the diagnosis of solitary thyroid nodules ?
If malignancy is suspected, given the high incidence of early metastases to the lungs
What is the use of CT/MRI in the diagnosis of solitary thyroid nodules ?
To analyze the extent of disease by scanning the neck and chest
State the main effects of trauma on the thyroid.
Trauma can give rise to cystic abscess
Why does exophthalmos occur in Grave’s associated hyperthyroidism ?
Because of the change in fat around the orbit, which reflects changes in the metabolism (i.e. change in thyroid hormones)
What are the main causes of hyperT ? How does it present ?
Grave’s (AI, may present as diffuse toxic goitre)
Functional goitre
Toxic adenoma
Overtreatment with Thyroxine
Transient neonatal thyrotoxicosis (mother with Graves Disease)
Describe the immunological mechanism behind Grave’s.
IgG antibodies against TSH receptor on thyrocytes, leading to antibody binding, which triggers cell to produce more thyroid hormones leading to toxicity
Antibodies are called thyroid-stimulating antibody (AKA LATS/TSI)
Describe epidemiology of Grave’s.
F more than M
What are the main causes of hypoT ?
-Congenital
-Autoimmune, due to:
Defective TH production either due to loss of parenchyma, or deficient TSH
