Thyroid Gland and Hormones Flashcards
Thyroid Gland is shaped like?
BUTTERFLY
Thyroid gland consists of ____ lobes, namely: ___ and ____ ; Which are connected by narrow band?
2; TRACHEA and LARYNX; ISTHMUS
How many weeks of gestation does thyroid gland begin to produce measurable amounts of hormone?
11
T/F
Does thyroid hormone play an important role?
TRUE
These hormones influence metabolic activity in the body
T3 and T4
T/F
All thyroid hormones DO NOT NEED IODINE to be formed
FALSE; ALL THYROID HORMONES ARE FORMED BY THE PRESENCE OF IODINE
Steps in regulation of Thyroid Gland
- Iodide
- Thyroid (oxidized)
- combined with Tyrosine
- Forms MIT and DIT
- coupled with T3 and T4
These are precursors or pro-hormones for the production of hormones.
MIT and DIT
Fundamental structural unit of the thyroid
gland
FOLLICLES
Follicles appear as ____; They are also shaped as _____; They rest in the _____ and rich in _____
tiny buds/ sacs; RING; basement membrane; GLYCOPROTEIN
The apex of the follicular cells has
MICROVILLI
2 Types of cells:
- Follicular cells
- Parafollicular cells
Type of cell that secretes T3 and T4 hormones
Follicular cells
T/F
Follicular cells produce some ACTIVE rT3 and rT4
FALSE; INACTIVE rT3 and rT4
Follicular cells have precursors namely?
MIT and DIT
Parafollicular cells is also known as
C cells
Type of cell that produces calcitonin
Parafollicular cells/ C cells
Physiologic Effects of Thyroid Hormones (6)
- Growth maturation and Sexual development
- Heat Production and Energy expenditure
- Influence carbohydrate, protein, and lipid metabolism
- Increase oxygen consumption.
- Increase heart rate.
- Increase blood volume.
This acts as preformed matrix containing tyrosyl groups.
THYROGLOBULIN
Thyroglobulin is stored in ____
It weighs about ____
follicular colloid of thyroid gland; 15-25 g
Steps in stimulating Thyroid hormone
- Hypothalamus
- secretes TRH
- stimulate anterior Pituitary
- secretes TSH
- stimulate Thyroid hormone
T/F
Is there a Positive feedback on hypothalamus and pituitary gland
FALSE; NEGATIVE FEEDBACK
It is the GRADUAL or SLOW decreasing release of hormones; narrow or maintain limits
NEGATIVE FEEDBACK
Percentage of T4 and T3 that is thyroid origin
100% T4 and 20% T3
Where is the 20% of T3 originates?
Enzymatically non-thyroidal tissues
What is Monodeionization?
T4 becoming T3
Classifications of Thyroid Glands
- Hyperthyroidism
- Hypothyroidism
- Euthyroidism
Hyperthyroidism is the ____ of thyroid hormones
EXCESS/ INCREASED
2 types of Hyperthyroidism
- Primary
- Secondary
Primary Hyperthyroidism PROFILE and gland that is abnormal
Increased T3, T4 and Decreased TSH; THYROID
Secondary Hyperthyroidism PROFILE and gland that is abnormal
Increased TSH, Pre-T4; PITUITARY
It is due to pituitary destruction of pituitary adenoma
Secondary Hyperthyroidism
Hyperthyroidism is caused by: (7)
- Graves’ disease – antibody present against TSH (antibody attacks TSH)
- Toxic adenoma – exposure to agents causing abnormalities.
- Toxic multinodular adenoma
- Exogenous iodine and Iodine-containing drugs.
- Ectopic thyroid tissue pituitary tumor
- TSH secreting pituitary tumor
- Thyroid cancer
Symptoms of Hyperthyroidism (6)
- Heat intolerance
- Tachycardia
- Weight loss
- Weakness
- Emotional inability
- Tremor
Conditions of Hyperthyroidism
- Thyrotoxicosis
- Thyroid Storm
A condition that is applied to a GROUP OF SYNDROMES caused by HIGH LEVELS OF FREE THYROID HORMONES in the circulation
THYROTOXICOSIS
Thyrotoxicosis PROFILE and is also known as:
TSH is low; FT₄ is normal but increased FT₃; Plummer’s disease
A condition that is rare and is destructive or severe when ignored
THYROID STORM
Hypothyroidism is the ____ of thyroid hormones
DECREASED
Hypothyroidism is treated with
thyroid hormone replacement therapy or levothyroxine
Hypothyroidism is caused by: (7) PAPACAR
- Pituitary/ hypothalamus
- Atrophic hypothyroidism
- Post-surgery
- Autoimmune hypothyroidism/ Hashimoto’s
- Congenital hypothyroidism
- Anti-thyroid drug therapy
- Radioactive therapy
3 types of Hypothyroidism
- Primary
- Secondary
- Tertiary
Primary Hypothyroidism PROFILE and gland that is abnormal
decreased T3 and T4; Increased TSH; THYROID
Primary Hypothyroidism is caused by
destruction or ablation of thyroid gland
Other causes of Primary Hypothyroidism
Surgical removal of the gland
Radiation exposure
Drugs like LITHIUM
Secondary Hypothyroidism PROFILE and gland that is abnormal
decreased T3, T4, TSH; PITUITARY
Tertiary Hypothyroidism PROFILE and gland that is abnormal
decreased T3, T4, TSH and TRH; HYPOTHALAMUS
Due to hypothalamic disease
Tertiary Hypothyroidism
Euthyroidism is a problem in ____ which makes it ____
rT3; INCREASED
Euthyroidism is caused by: (3)
- Presence of goiter
- Thyroid adenoma
- Thyroid carcinoma
Major component of thyroid hormone
IODINE
Major source of IODINE
DIET
Additional source of IODINE
DEIONIZATION
Conversion of thyroid hormones:
LIVER, KIDNEYS; T4 – T3
Hormones which THYROID DO NOT ENTER CELLS and is Biologically inert
Protein bound thyroid hormones
T/F
Protein-bound thyroid hormones acts as RESERVOIR for circulating thyroid hormones
TRUE
Hormones that are a Physiologically active form of thyroid hormones and it readily enter cells; exert biological effects
Free thyroid hormones
REGULATES production and secretion of thyroid hormone
Hypothalamic-Pituitary-Thyroid axis or HPTA
MAIN THYROID HORMONE released from thyroid gland.
THYROXINE or Total T4
Reference range for THYROXINE or Total T4 is
5-12.5 ug/dL (adults)
Distribution of THYROXINE or Total T4
- 70% of T4: bound to thyroid binding globulin (TBG)
- 20% of T4: bound to Transthyretin/Prealbumin.
- 10% of T4: bound to albumin
Thyroid disorders and their relation to Total T4
- Primary hypothyroidism
- Hyperthyroidism
- T4 thyrotoxicosis
- Low T3 and low T4 syndrome
Primary hypothyroidism PROFILE in Total T4
decreased T4; increased TSH
Hyperthyroidism PROFILE in Total T4
increased T3 and T4; decreased TSH
T4 thyrotoxicosis PROFILE in Total T4
increased T4; normal serum T3
Low T3 and low T4 syndrome PROFILE in Total T4
decreased T3 and T4
Analytical method for THYROXINE or Total T4
IMMUNOASSAY (Ab reagent)
Reference Interval of Thyroxine/ Total T4
5-12.5 ug/dL (71-161 mmol/L)
A CLASSICAL METHOD of adjusting a total T4 measurement for ALTERATIONS in binding protein
T3 uptake test
Biologically active fraction of T4 in circulating blood
FREE THYROXINE/ Free T4
Thyroid disorders and their relation to FT4
- Hyperthyroidism: increased or high FT4
- Hypothyroidism: decreased or low FT4
Reference method of measurement for Free thyroxine/ Free T4 is
Equilibrium dialysis
Other methods of measurement for Free thyroxine/ Free T4
- ULTRAFILTRATION
- SYMMETRICAL dialysis
- MASS SPECTROMETRY
- IMMUNOASSAYS
- FT4 INDEX
A free T4 method that uses PRESSURE to push the plasma sample through a dialysis membrane
ULTRAFILTRATION
A free T4 method that plasma is DIALYZED against itself, using a radioactive tracer added on one side to measure the rate of diffusion of FT4 which is proportional to its concentration.
SYMMETRICAL dialysis
A free T4 method that simultaneously measures FT4 and FT3.
MASS SPECTROMETRY
A free T4 method that is from total T4 and unbound T4 sites serum proteins
FT4 INDEX
MAJOR THYROID HORMONES
- T3
- rT3
- T4
Also known as: 3,5,3’ triiodothyronine
T3 or TRIIODOTHYRONINE
Most active thyroid hormone
T3 or TRIIODOTHYRONINE
T/F
T3 or triiodothyronine is MORE tightly bound to serum proteins than T4
FALSE; LESS
Greater proportion of T3 exists in 3 forms namely:
- Free form
- Diffusible state
- Protein-bound
Production of T3 or TRIIODOTHYRONINE
80% – produced outside the thyroid (tissue) through the deionization process.
20% - formed within thyroid gland
The principal application of T3 or TRIIODOTHYRONINE
Diagnosis of T3 thyrotoxicosis