BIO201L Straightline
Endocrine System
Pre Lab Questions
(With Solutions)
2025
1
,1. A 45-year-old patient presents with chronic hyperglycemia and is
prescribed insulin therapy. Through which mechanism does the
insulin receptor primarily transmit its signal?
A. G-protein–coupled receptor activating IP₃/DAG pathway
B. Ligand-gated ion channel increasing intracellular calcium
C. Receptor tyrosine kinase initiating autophosphorylation
D. Nuclear receptor modulating gene transcription
E. Cytokine receptor activating JAK/STAT pathway
ANS: C
Rationale: The insulin receptor is a receptor tyrosine kinase. Binding
of insulin triggers autophosphorylation of tyrosine residues and
downstream signaling that promotes glucose uptake into cells.
---
2. A patient with Cushing’s disease undergoes a low-dose
dexamethasone suppression test. Which result indicates pituitary-
dependent Cushing’s disease rather than an adrenal adenoma?
A. Cortisol remains elevated after dexamethasone
B. ACTH levels drop and cortisol is suppressed
C. ACTH increases and cortisol increases
D. Cortisol suppression only with high-dose dexamethasone
E. Cortisol and ACTH remain unchanged
ANS: D
Rationale: In pituitary Cushing’s (Cushing’s disease), a high-dose
dexamethasone test will suppress ACTH release from the pituitary,
lowering cortisol. In adrenal adenomas, cortisol remains elevated
despite high-dose dexamethasone.
---
3. A patient has hypocalcemia with elevated parathyroid hormone
2
, (PTH). Which action of PTH most directly raises serum calcium?
A. Increasing bone collagen synthesis
B. Stimulating urinary calcium excretion
C. Promoting osteoclast-mediated bone resorption
D. Reducing activation of vitamin D in the kidney
E. Inhibiting intestinal calcium absorption
ANS: C
Rationale: PTH increases serum calcium primarily by stimulating
osteoclast activity, which releases calcium from bone into the
bloodstream.
---
4. A patient presents with elevated T3/T4 and low TSH. This laboratory
pattern is most consistent with which disorder?
A. Primary hyperthyroidism
B. Secondary hyperthyroidism
C. Tertiary hypothyroidism
D. Euthyroid sick syndrome
E. Primary hypothyroidism
ANS: A
Rationale: Primary hyperthyroidism (for example, Graves’ disease)
features elevated thyroid hormones with suppressed TSH via negative
feedback on the pituitary.
---
5. Growth hormone (GH) exerts many of its effects through insulin-
like growth factor 1 (IGF-1). Where is IGF-1 primarily produced?
A. Anterior pituitary
B. Hypothalamus
C. Skeletal muscle
D. Liver
3
Endocrine System
Pre Lab Questions
(With Solutions)
2025
1
,1. A 45-year-old patient presents with chronic hyperglycemia and is
prescribed insulin therapy. Through which mechanism does the
insulin receptor primarily transmit its signal?
A. G-protein–coupled receptor activating IP₃/DAG pathway
B. Ligand-gated ion channel increasing intracellular calcium
C. Receptor tyrosine kinase initiating autophosphorylation
D. Nuclear receptor modulating gene transcription
E. Cytokine receptor activating JAK/STAT pathway
ANS: C
Rationale: The insulin receptor is a receptor tyrosine kinase. Binding
of insulin triggers autophosphorylation of tyrosine residues and
downstream signaling that promotes glucose uptake into cells.
---
2. A patient with Cushing’s disease undergoes a low-dose
dexamethasone suppression test. Which result indicates pituitary-
dependent Cushing’s disease rather than an adrenal adenoma?
A. Cortisol remains elevated after dexamethasone
B. ACTH levels drop and cortisol is suppressed
C. ACTH increases and cortisol increases
D. Cortisol suppression only with high-dose dexamethasone
E. Cortisol and ACTH remain unchanged
ANS: D
Rationale: In pituitary Cushing’s (Cushing’s disease), a high-dose
dexamethasone test will suppress ACTH release from the pituitary,
lowering cortisol. In adrenal adenomas, cortisol remains elevated
despite high-dose dexamethasone.
---
3. A patient has hypocalcemia with elevated parathyroid hormone
2
, (PTH). Which action of PTH most directly raises serum calcium?
A. Increasing bone collagen synthesis
B. Stimulating urinary calcium excretion
C. Promoting osteoclast-mediated bone resorption
D. Reducing activation of vitamin D in the kidney
E. Inhibiting intestinal calcium absorption
ANS: C
Rationale: PTH increases serum calcium primarily by stimulating
osteoclast activity, which releases calcium from bone into the
bloodstream.
---
4. A patient presents with elevated T3/T4 and low TSH. This laboratory
pattern is most consistent with which disorder?
A. Primary hyperthyroidism
B. Secondary hyperthyroidism
C. Tertiary hypothyroidism
D. Euthyroid sick syndrome
E. Primary hypothyroidism
ANS: A
Rationale: Primary hyperthyroidism (for example, Graves’ disease)
features elevated thyroid hormones with suppressed TSH via negative
feedback on the pituitary.
---
5. Growth hormone (GH) exerts many of its effects through insulin-
like growth factor 1 (IGF-1). Where is IGF-1 primarily produced?
A. Anterior pituitary
B. Hypothalamus
C. Skeletal muscle
D. Liver
3
