Q: Given the equation for metabolic rate $$\text{Metabolic Rate} = \frac{\text{mL O_2$ consumed in 1 hour}}{\text{mass in kg}}$$, calculate the metabolic rate for a rat that consumes 900 mL O$$_2 in 1 $$hour and weighs 0.5 kg.

$$1800\ \text{mL O}_2/\text{kg}/\text{hr}$$

Question 1

Which hormone is directly responsible for stimulating the thyroid gland to release thyroxine, and what would happen to a thyroidectomized rat's metabolic rate after TSH injection?

Accepted Answer

Thyroid-stimulating hormone (TSH); metabolic rate would remain unchanged

Question 2

A patient presents with high cortisol and low ACTH levels. Based on the HPA axis, which disorder is most likely?

Accepted Answer

Cushing's Syndrome

Question 3

Given the equation for metabolic rate $$	ext{Metabolic Rate} = \frac{	ext{mL O_2$ consumed in 1 hour}}{	ext{mass in kg}}$$, calculate the metabolic rate for a rat that consumes 900 mL O$$_2 in 1 $$hour and weighs 0.5 kg.

Accepted Answer

$$1800\ 	ext{mL O}_2/	ext{kg}/	ext{hr}$$

Question 4

Which of the following best describes the effect of propylthiouracil (PTU) on a normal rat's thyroid function and metabolic rate?

Accepted Answer

PTU blocks thyroxine production, decreasing metabolic rate and causing goiter

Question 5

A blood sample has an optical density (OD) of 0.4. Using the standard curve data (OD 0.1 = 70 mg/dL, 0.2 = 80 mg/dL, 0.3 = 90 mg/dL, 0.4 = 100 mg/dL, 0.5 = 110 mg/dL), what is the glucose concentration?

Accepted Answer

100 mg/dL

Question 6

Which hormone is released when blood glucose levels fall, and what is its primary effect on the liver?

Accepted Answer

Glucagon; stimulates glycogen breakdown to glucose

Question 7

A patient with a fasting plasma glucose level of 130 mg/dL would be classified as having which condition?

Accepted Answer

Diabetes Mellitus

Question 8

Which treatment most effectively improved bone density in ovariectomized rats with osteoporosis, and what is the mechanism?

Accepted Answer

Estrogen; inhibits osteoclasts and stimulates osteoblasts

Question 9

In the HPA axis, what is the expected ACTH and cortisol profile in secondary adrenal insufficiency?

Accepted Answer

Low ACTH, low cortisol

Question 10

Which laboratory technique is depicted in the image with a solvent, pump, injector, HPLC column, detector, and waste, and what is its primary use in hormone analysis?

Accepted Answer

High-performance liquid chromatography (HPLC); separating and quantifying hormones like cortisol and ACTH

Question 11

A hypophysectomized rat receives a thyroxine injection. What is the expected effect on its metabolic rate and why?

Accepted Answer

Increase; thyroxine acts directly on target cells to raise metabolic rate

Question 12

Which of the following best explains why goiter can develop in a rat after TSH or PTU injection?

Accepted Answer

TSH stimulates thyroid growth; PTU blocks thyroxine synthesis, causing compensatory thyroid growth

Question 13

Which of the following is a key difference between Type 1 and Type 2 Diabetes Mellitus?

Accepted Answer

Type 1 is due to lack of insulin production; Type 2 is due to insulin resistance

Question 14

If a sample solution in a spectrophotometer absorbs more light, what happens to its optical density (OD) and what does this indicate about the concentration of the analyte?

Accepted Answer

OD increases; analyte concentration increases

Question 15

Which hormone is released from the anterior pituitary in response to CRH and stimulates the adrenal cortex to produce cortisol?

Accepted Answer

ACTH

Question 16

A patient has low cortisol and high ACTH levels. Which disorder is most likely, and what is the underlying cause?

Accepted Answer

Addison's Disease; destruction of adrenal cortex

Question 17

Which of the following best describes the negative feedback mechanism in the HPA axis?

Accepted Answer

High cortisol inhibits CRH and ACTH release

Question 18

Which of the following is a direct effect of estrogen therapy in ovariectomized rats with osteoporosis?

Accepted Answer

Inhibition of osteoclasts and stimulation of osteoblasts

Question 19

If a rat's baseline metabolic rate is 1500 mL O$$_2/kg/hr $$and after thyroxine injection it increases to 1800 mL O$$_2/kg/hr$$, what is the percent increase in metabolic rate?

Accepted Answer

$$\frac{1800-1500}{1500} 	imes 100 = 20\%$$

Endocrine Physiology and Experimental Analysis: Thyroid, Glucose, Bone, and HPA Axis

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