Thyroid and and Parathyroid Function Flashcards Preview

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Flashcards in Thyroid and and Parathyroid Function Deck (79)
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What's a Positive Feedback Loop?

Positive Feedback Loop – increase in one action triggers increase in target​


Example of a (+) Feedback Loop

Childbirth contractions trigger oxytocin, which in turn amplifies the contractions​


What's a Negative Feedback Loop?

Negative Feedback Loop – response is opposite to the perturbation​


Example of a (-) Feedback Loop

Pituitary TSH and thyroid T4


What are the glands responsible for regulating the activity of the Thyroid?

Hypothalamus and pituitary regulate thyroid, as well as intrinsic regulation by the gland itself​


How does Hypothalamus and Pituitary regulate Thyroid activity?

Hypothalamus produces thyroid releasing hormone (TRH), which acts on anterior pituitary​

Thyroid stimulating hormone (TSH) released by anterior pituitary into blood stream​


What are the 3 thyroid hormones?

Triiodothyronine (T3)​
Thyroxine (T4)​
Calcitonin​ (Weak effect on calcium-phosphorus balance​)


Function of T3 and T4 (2)

T3 and T4
-regulate metabolic rate of body
-increase protein synthesis​


What is Calcitonin's function?

Weak effect on calcium-phosphorus balance​


Name 2 routes that aid in Thyroid stimulation:

Vascular supply (iodine) and Sympathetic nervous system​


Trace the mechanism of Thyroid stimulation (negative loop) from the Iodine in the blood stream to the TRH from the hypothalamus.

Iodine traveling in blood (from diet) absorbed into thyroid follicle cell to combine with Thyroglobulin (TGB) to form T3 and T4 (thyroid hormones)​

Stimulated by TSH released by anterior pituitary into blood stream​

Stimulated initially by hypothalamus TRH​


What's the best stimulus for TRH?

Exposure to cold


What's the end result of the Thyroid negative feedback loop?

Negative feedback loop control​
T3 and T4 in circulation limit production​


Name 4 major actions of T3 and T4.

1. Enter cell and bind with receptors in nucleus​
DNA stimulated for gene expression​
Altered protein synthesis within cells​

2. Brain growth and development​

3. Bone growth and development​

4. Function of metabolism, cardiac system, heat production, glucose and fat metabolism​


What are the 3 main functions of the Thyroid?

Metabolism, growth, and development​


Explain how is Thyroid involved in metabolism?

Increase thermogenesis
Basal metabolic rate and heat production​

Metabolic effect- Energy substrate utilization​
Glucose absorption and enzyme enhancement​
Lipolysis and lipolytic hormone use​


Explain how is Thyroid involved in growth and development?

Growth and development
Stimulate GH release and enhanced effects​


What is the cardiovascular effect of Thyroid activity?

Cardiovascular effects:
Increase HR and contractility possibly by enhancing effect of epi and norepi​ (release by the medulla of adrenal glands)


What are some confounding variables when trying to diagnose Thyroid dysfunction at an older age?

After age 60, thyroid may be mistaken for dementia, depression, heart disease​


Name 3 risk factors for Thyroid dysfunction

family history
age (>50)
gender (female)​


Name a few effects of alterations in Thyroid functioning

Alterations in thyroid can produce changes in hair, nails, skin, eyes, GI, respiratory tract, cardiovascular, neuromuscular, musculoskeletal systems – virtually everything​


What test diagnoses thyroid dysfunction​?

TSH (thyroid stimulating hormone) test


What is the normal range of TSH?

0.5 - 4.70 µIU/mL​


Name 8 sets of characteristics specific to hypothyroidism

Fatigue, feeling run down or tired, difficulty concentrating, depression, slowed heart beats

Non tender swelling around the neck

Muscle cramps, muscle weakness

weight gain

dry, coarse itchy skin
dry, coarse thinning hair

intolerance to cold especially in the hands and feet

increased menstrual flow, irregular periods, infertility / miscarriage



Name 8 sets of characteristics specific to hyperthyroidism

Nervousness, irritability, restlessness, increased perspiration, palpitation, insomnia, heart racing, panic

Non tender swelling around the neck

Muscular weakness and tremor especially the upper arms and thighs. In later Grave's disease eyes may bulge

weight loss

thinning skin
fine and brittle hair

intolerance to heat

less frequent periods with lighter flow

frequent bowel movements


Describe hormonal levels in hypothyroidism

High TSH, low T3, T4
Antibodies to TPO in Hashimoto's thyroiditis


Describe hormonal levels in hyperthyroidism

Low TSH, High T3, T4
Antibodies to TSH receptors in Grave's disease


Goiter ...........

Goiter, enlargement commonly due to lack of iodine in diet​


Describe the feedback loop present in goiter in relation to dietary lack of iodine

Inhibits normal thyroid hormone production, causing hypersecretion of TSH due to lack of negative feedback loop​
Almost eradicated in US due to iodized salt​


clinical presentation of goiter

Would see increased neck size, pressure on trachea and esophagus, dysphagia, hoarseness, difficulty breathing​