Thyroid Gland and Hormones Quiz

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Questions and Answers

What is the expected normal range for radioactive iodine uptake after 24 hours?

15 - 35 %

5 - 30 % (correct)

10 - 40 %

0 - 25 %

Which of the following is NOT a clinical feature of acromegaly?

Deep and husky voice

Enlarged soft tissues

Regular menstrual cycles (correct)

Prognathism

What is the primary function of growth hormone in the body?

Decrease protein synthesis

Reduce free fatty acids

Increase blood glucose levels (correct)

Enhance digestive enzymes

Which condition is primarily caused by an adenoma of the pituitary gland?

Acromegaly Signup and view all the answers

Which of the following hormones is primarily affected in Cushing syndrome?

Cortisol Signup and view all the answers

What complication may result from an untreated pituitary tumor?

Sensory disturbances and weakness Signup and view all the answers

Which of the following is a feature of the adrenal medulla's secretion?

Epinephrine Signup and view all the answers

Which of the following is a common cause of Cushing syndrome?

Pituitary adenoma causing ACTH overproduction Signup and view all the answers

What is the primary function of thyroid-stimulating hormone (TSH)?

Regulates thyroid hormone production, secretion, and growth. Signup and view all the answers

What is thyrotoxicosis primarily associated with?

High levels of circulating thyroid hormones. Signup and view all the answers

Which sign is characterized by the upper eyelid lagging behind the eyeball when looking downward?

Von Graefe's sign Signup and view all the answers

Which of the following symptoms is NOT typically associated with hyperthyroidism?

Weight gain Signup and view all the answers

What commonly happens in the absence of TSH due to negative feedback from T4 and T3?

Thyroid hormone levels decrease. Signup and view all the answers

Which symptom is more likely to be experienced by someone with hypothyroidism?

Cold sensitivity Signup and view all the answers

How is thyroid function initially evaluated?

Measurement of T4 and T3 levels. Signup and view all the answers

Which of the following statements regarding hyperthyroidism is accurate?

It can cause an increased heart rate and anxiety. Signup and view all the answers

What symptom is commonly associated with adrenal malignancy due to ectopic ACTH secretion?

Mood changes Signup and view all the answers

Which of the following is a potential outcome of primary adrenal insufficiency (Addison's Disease)?

Hyperpigmentation Signup and view all the answers

Which sign is most indicative of Cushing's syndrome?

Stria rubra Signup and view all the answers

What is a common effect of hyperparathyroidism due to hypercalcemia?

Constipation Signup and view all the answers

What is the primary stimulus for parathormone (PTH) secretion?

Hypocalcemia Signup and view all the answers

What symptom is most likely associated with secondary adrenal insufficiency?

Nausea and vomiting Signup and view all the answers

Which of the following is NOT a sign associated with adrenal malignancy?

Hyperpigmentation Signup and view all the answers

Which gland is responsible for secreting parathormone (PTH)?

Parathyroid gland Signup and view all the answers

Which of the following is a primary secretory product of the thyroid gland?

Thyroxine (T4) Signup and view all the answers

What percentage of circulating T3 is derived from the deiodination of T4 in peripheral tissues?

80% Signup and view all the answers

Which hormone primarily influences cell differentiation, growth, and metabolism?

Thyroxine (T4) Signup and view all the answers

What is the recommended minimum daily intake of iodine for adults?

150 µg/day Signup and view all the answers

What role does T3 play in skeletal maturation?

It regulates the expression of factors for linear growth. Signup and view all the answers

Which plasma carrier protein binds the highest percentage of circulating T4?

Thyroxine-binding globulin (TBG) Signup and view all the answers

What is the effect of thyroid hormone on basal metabolic rate?

It increases the basal metabolic rate. Signup and view all the answers

Which of the following hormones is secreted by parafollicular cells in the thyroid gland?

Calcitonin Signup and view all the answers

What role does free hormone play in the body?

It is responsible for metabolic activity and physiological effects. Signup and view all the answers

Which of the following effects is NOT associated with thyroid hormones?

Decrease in gut motility Signup and view all the answers

What is a consequence of calcium deposition in the renal tubules?

Development of renal stones Signup and view all the answers

Which of the following is a clinical manifestation of hypoparathyroidism?

Carpopedal spasm Signup and view all the answers

Which lab findings are indicative of hypoparathyroidism?

Decreased serum calcium and increased phosphate Signup and view all the answers

What is a common treatment for hypercalcemia?

Hydration and medications to lower calcium levels Signup and view all the answers

Which symptom is associated with nephrocalcinosis?

Severe pruritus Signup and view all the answers

What is a common symptom of hypercalcemia?

Coma and stupor Signup and view all the answers

What indicates a failure of PTH secretion?

Surgical removal of thyroid glands Signup and view all the answers

Which of the following can lead to impaired mentation and memory loss?

Hypoparathyroidism Signup and view all the answers

Study Notes

Thyroid Gland and Thyroid Hormones

The thyroid gland secretes thyroid hormones and calcitonin, crucial for calcium homeostasis.
The follicles are the functional units of the thyroid gland.
The thyroid produces T4 (thyroxine) and T3 (triiodothyronine), which are essential for cell differentiation, growth, and metabolism.
Iodine is a crucial element for thyroid hormone synthesis and is obtained through various foods, supplements, and iodized salt.
T4 is the primary product of the thyroid gland, while T3 is mostly derived from T4 deiodination in peripheral tissues.
Carrier proteins (TBG, TTR, albumin) bind over 99% of circulating T4 and T3, with only the unbound (free) hormone having metabolic activity.

Thyroid Hormone Action

Thyroid hormone plays a vital role in various bodily functions, including:
- fetal brain and skeletal maturation
- increasing basal metabolic rate
- influencing cardiovascular function (inotropic and chronotropic effects)
- enhancing sensitivity to catecholamines
- stimulating gut motility
- increasing bone turnover
- affecting blood glucose and cholesterol levels

Control of Thyroid Function

The hypothalamic-pituitary-thyroid axis regulates thyroid hormone production and secretion.
The hypothalamus secretes TRH (thyroid-releasing hormone), which stimulates the anterior pituitary to release TSH (thyroid-stimulating hormone).
TSH promotes thyroid hormone synthesis and secretion.
Negative feedback by T4 and T3 regulates the axis, ensuring proper thyroid hormone levels.

Thyroid Disorders

Hypothyroidism occurs when the thyroid gland is underactive, leading to reduced thyroid hormone production.
- Symptoms include:
  - dry hair
  - puffy face
  - slow heart beat
  - weight gain
  - constipation
  - brittle nails
  - cold intolerance
  - depression
  - fatigue
  - memory loss
  - heavy menstrual periods
  - muscle aches
Hyperthyroidism occurs when the thyroid gland is overactive, leading to increased thyroid hormone production.
- Symptoms include:
  - hair loss
  - bulging eyes
  - sweating
  - rapid heart beat
  - weight loss
  - regular gas
  - soft nails
  - sleep difficulties
  - heat intolerance
  - infertility
  - irritability
  - muscle weakness
  - nervousness
  - scant menstrual periods

Evaluation of Thyroid Function

Laboratory tests are essential for evaluating thyroid function:
- total T4, T3, free T4, and free T3 measurements
- radioactive iodine uptake (RAIU) to assess thyroid gland activity
- serum TSH to assess pituitary function
Imaging studies may also be helpful:
- thyroid ultrasound to visualize the gland
- fine needle aspiration biopsy for cytological diagnosis

Pituitary Gland

The pituitary gland secretes various hormones, including growth hormone (GH).
GH plays a crucial role in growth, metabolism, and cellular processes.
Acromegaly is a condition characterized by excessive GH secretion, resulting in abnormal growth and enlarged features.
- Clinical manifestations include:
  - coarse facial features
  - enlarged hands and feet
  - thickened skin with increased hair growth
  - deep and husky voice
  - joint pain
  - cardiovascular complications (cardiomegaly, hypertension)
  - compression of nerves causing sensory and motor disturbances
  - headaches

Adrenal Gland Disorders

The adrenal gland produces cortisol, mineralocorticoids, and androgens from the cortex, and adrenaline from the medulla.
Adrenocortical hormones are essential for:
- nutrient metabolism
- circulatory system function
- muscle function
- blood cell production
- skeletal system maintenance
- brain and nerve function
- immune system function

Cushing's Syndrome

Cushing's syndrome is characterized by excessive cortisol levels in the blood.
Etiologies include:
- iatrogenic (steroid therapy)
- pituitary adenoma (ACTH-secreting)
- adrenal tumors (cortisol-secreting)
- ectopic ACTH production (e.g., small cell lung cancer)

Cushing's Syndrome Symptoms

Symptoms include:
- mood changes (depression, euphoria)
- easy bruising
- weakness
- weight gain
- amenorrhea
- back pain
Signs include:
- truncal obesity
- moon face
- buffalo hump
- striae rubra
- hypertension
- osteoporosis
- thin, fragile skin
- diabetes
- hirsutism (abnormal hair growth)

Hypofunction of the Adrenal Gland

Adrenal insufficiency (Addison's disease) is characterized by an insufficient production of adrenal hormones.
Etiologies include:
- secondary (pituitary insufficiency)
- primary (adrenal gland failure) due to:
  - destruction (tuberculosis, fungal infections, amyloidosis, hemochromatosis)
  - tumor
  - autoimmune process

Adrenal Insufficiency Symptoms

Symptoms include:
- weakness, fatigue, dizziness
- nausea, vomiting, weight loss
- diarrhea, dehydration
- salt craving
- abdominal pain

Adrenal Insufficiency Signs

Signs include:
- hyperpigmentation: darkening of skin, buccal mucosa
- hypotension
- reduced hair growth
- dehydration signs

Parathyroid Gland

The parathyroid glands secrete parathyroid hormone (PTH), which regulates calcium levels in the blood.
Hypocalcemia stimulates PTH secretion.
Hyperparathyroidism occurs when the parathyroid glands are overactive, leading to excessive PTH production and hypercalcemia.

Hyperparathyroidism Symptoms

Many patients are asymptomatic.
Symptoms may be non-specific, such as weakness, fatigue, and easy fatigueability.
Symptoms due to hypercalcemia:
- anorexia, nausea, vomiting, dyspepsia, constipation
- increased risk of peptic ulcer disease and pancreatitis
- interstitial nephritis leading to polyuria, polydipsia, nocturia
- renal stones (calcium oxalate and phosphate stones) leading to renal colic and UTIs
- nephrocalcinosis (kidney calcification)
- impaired mentation, memory loss, emotional lability, depression
- weakness, arthralgia
- severe pruritus (calcification of the skin)
- bone resorption leading to cysts, brown tumors, subperiosteal erosion

Hyperparathyroidism Diagnosis

Laboratory tests:
- hypercalcemia
- hypophosphatemia
- increased alkaline phosphatase
- increased PTH levels
- urinalysis and kidney X-ray
- bone density test

Hyperparathyroidism Treatment

Medical treatment to manage hypercalcemia
Surgical removal of overactive parathyroid glands

Hypoparathyroidism

Hypoparathyroidism occurs when there is a failure of PTH secretion, leading to hypocalcemia.
Causes:
- surgical (thyroidectomy, neck exploration, removal of neck cancer)
- transient (after removal of a parathyroid adenoma)
- idiopathic (autoimmune)
- prolonged hypomagnesemia

Hypoparathyroidism Clinical Picture

Asymptomatic or manifestations of hypocalcemia:
- neuromuscular activity: numbness, tingling around the mouth and lips, paresthesias in the hands and feet
- bronchospasm, laryngeal spasm (stridor)
- carpopedal spasm

Hypoparathyroidism Diagnosis

Laboratory tests:
- decreased serum calcium
- increased phosphate (in the absence of renal failure)
- decreased PTH levels

References

Step-Up to Medicine, 5th edition
Davidson’s Principles & Practice of Medicine, 23rd edition

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Description

Test your knowledge on the thyroid gland, its hormones, and their functions. This quiz covers the critical aspects of T3 and T4 production, the importance of iodine, and the roles of thyroid hormones in growth and metabolism. Explore the intricate details of thyroid function and hormone action.