Thyroidea Flashcards
Where is the thyroid gland located?
In the larynx.
What hormones are produced by the thyroid gland?
T4 (thyroxine) – inactive, converted to active T3, and T3 (triiodothyronine) – biologically active form.
What are the main functions of thyroid hormones?
Adjust metabolic rate, increase protein synthesis, and regulate growth and development.
How are thyroid hormones transported in the blood?
Bound to Thyroid Binding Globulin (TBG).
How is thyroid hormone production regulated?
- Hypothalamus releases TRH.
- TRH stimulates anterior pituitary to release TSH.
- TSH stimulates thyroid to produce T3 and T4.
What are the effects of thyroid hormones?
Cardiovascular: Positive inotropic and chronotropic effects.
Sympathetic activation: Increases adrenergic receptor sensitivity.
Respiration: Enhances oxygen utilization.
Hematopoiesis: Stimulates red blood cell production.
Bones: Increases turnover and growth.
Muscles: Enhances contraction and relaxation.
What is hypothyroidism?
Hypothyroidism is a tyroid hormone deficiency which can be either congenital, present at birth, or aquired through one of the primary or secondary reasons.
There are two types of hypothyroidisms what are they? and when/how do they develop?
Aquired Hypothyroidism and Congenital hypothyroidism
What are the causes of Aquired hypothyroidism?
Primary: Autoimmune diseases, iodine deficiency, radiation, enzyme defects.
Secondary: Pituitary TSH deficiency.
Tertiary: Hypothalamic dysfunction.
What are the clinical manifestations of aquired hypothyroidism?
Metabolic: Fatigue, weight gain, cold intolerance.
Dermatological: Dry skin, hair loss, myxedema.
Neurological: Depression, slowed cognition.
Cardiovascular: Bradycardia, hypercholesterolemia.
Musculoskeletal: Weakness, joint pain.
What is the pathophysiology of Aquired hypothyroidism?
Low thyroid hormones lead to decreased metabolic rate, myxedema, and hypercholesterolemia.
What causes congenital hypothyroidism?
Absence of the Thyroid Gland (thyroid agenesis).
Abnormal Thyroid Hormone Biosynthesis: Genetic defects affecting hormone production.
TSH Deficiency: Impaired thyroid stimulation due to pituitary or hypothalamic dysfunction.
What are the clinical manifestations of congenital hypothyroidism?
Cretinism (Medfødt jodmangelsyndrom): Congenital hypothyroidism causes intellectual disability and impairs physical growth.
What is cretinism?
A condition caused by untreated congenital hypothyroidism leading to severe developmental delays and stunted growth.
Describe how congenital hypothyroidism can be treated and its effects on the most serious clinical manifestation.
Congenital hypothyroidism is treated by thyroid hormone replacement.
When early and adequate thyroid hormone replacement treatment is implemented for congenital hypothyroidism, the risk of intellectual disability is very low.
What is hyperthyroidism ( Thyrotoxicosis )?
Excess thyroid hormone production causing increased metabolic activity.
What are the causes of hyperthyroidism?
Primary: Graves disease (80% cases), multinodular goiter.
Secondary: Pituitary adenoma.
Thyroiditis: Inflammation causing hormone leakage.
What is the pathophysiology of hyperthyroidism, Graves disease?
Graves disease is an autoimmune disorder characterized by abnormal stimulation of the thyroid gland by thyroid-stimulating antibodies (TSH receptor antibodies) that act through (/activate) (the normal) TSH receptors
Autoimmune antibodies stimulate the thyroid to overproduce T3/T4.
What are the clinical manifestations of hyperthyroidism?
Metabolic: Hypermetabolism, weight loss, heat intolerance.
Sympathetic Effects: Tachycardia, palpitations, sweating.
Musculoskeletal: Tremors, muscle cramps.
Dermatological: Thin, silky hair.
Eyes (Graves): Ophthalmopathy – bulging eyes, risk of vision loss.
How could Thyrotoxicosis be treated?
Reducing the amount of thyroid hormone. The gland can be partially or fully removed surgically.
What tests are used to evaluate thyroid function?
TSH Levels:
High TSH: Primary hypothyroidism.
Low TSH: Primary hyperthyroidism or secondary hypothyroidism.
T3 and T4 Levels:
Total (bound and free) and Free (active, unbound).
Newborn Screening:
Detects congenital hypothyroidism early.
How do tests distinguish primary vs secondary thyroid disorders?
Primary disorders have abnormal T3/T4 with opposite TSH levels, while secondary disorders have abnormal T3/T4 with matching TSH levels.
