MLT GlobePhysiology: Endocrine physiology
40 Physiology MCQs on Endocrine physiology with answers and explanations.
Which system controls body functions mainly by releasing hormones into the blood?
Endocrine glands secrete hormones that travel in the blood to target cells. The nervous system relies mainly on electrical signals and local neurotransmitters.
Which hormone is NOT made by the anterior pituitary?
Parathyroid hormone comes from the parathyroid chief cells. The anterior pituitary secretes GH, PRL, TSH, ACTH, FSH and LH.
A lab measures a steroid responsible for male secondary sex characteristics. Which hormone belongs to the androgen class?
Androgens are male sex steroids such as testosterone and DHEA. Cortisol is a glucocorticoid.
A patient passes large volumes of dilute urine, yet blood and urine glucose are normal. Which hormone is deficient or ineffective?
Diabetes insipidus is due to lack of ADH (central) or renal resistance to it (nephrogenic), giving low urine osmolality. Diabetes mellitus involves insulin and glycosuria.
A patient with weight loss, heat intolerance and tachycardia has a raised basal metabolic rate. Excess of which hormones best explains this?
T3 and T4 increase oxygen consumption and heat production in most tissues, so hyperthyroidism raises BMR. The others have no major metabolic-rate effect.
A patient with suspected hyperthyroidism is being assessed. Which finding would NOT fit this diagnosis?
Excess thyroid hormone raises metabolism and gut motility, typically causing diarrhoea or frequent stools. Constipation is characteristic of hypothyroidism.
Which gland releases melatonin, mainly at night, to regulate the sleep-wake cycle?
The pineal gland secretes melatonin in darkness, helping set circadian rhythms. Light falling on the retina suppresses its release.
In the pancreatic islets, which cells produce glucagon?
Alpha cells secrete glucagon, beta cells insulin, delta cells somatostatin, and PP cells pancreatic polypeptide.
In primary hypothyroidism caused by failure of the thyroid gland, serum TSH is typically:
Low free T4 removes negative feedback, so the pituitary secretes more TSH. Raised TSH is the most sensitive screening test. In secondary (pituitary) hypothyroidism TSH is low or inappropriately normal.
A patient with thyrotoxicosis is anxious, restless and has brisk reflexes. This reflects which effect of thyroid hormone on the nervous system?
Excess thyroid hormone increases CNS excitability, causing nervousness, tremor, insomnia and hyperreflexia. Deficiency causes slowed thinking and sluggish reflexes.
In Graves' disease, which change would NOT be expected?
TSH-receptor antibodies drive excess thyroid hormone, raising metabolic rate, appetite and heat production while causing weight loss and muscle weakness. A low metabolic rate occurs in hypothyroidism.
Aldosterone-secreting cells lie in which zone, the outermost layer of the adrenal cortex?
From outside in: glomerulosa (mineralocorticoids), fasciculata (glucocorticoids), reticularis (androgens). The medulla is not part of the cortex.
After a carbohydrate-rich meal, blood glucose rises. Which hormone do pancreatic beta cells release in response?
Beta cells secrete insulin when glucose rises, promoting uptake and storage. Glucagon, cortisol and growth hormone all raise blood glucose.
A patient with chronically raised serum cortisol shows central obesity, purple striae and hyperglycaemia. This picture is:
Cushing syndrome results from prolonged glucocorticoid excess. Addison disease is cortisol deficiency; Conn syndrome is primary hyperaldosteronism.
Which of these hormones is synthesised from the amino acid tyrosine?
Catecholamines (dopamine, norepinephrine, epinephrine) and thyroid hormones derive from tyrosine. ACTH and insulin are peptides; cortisol is a cholesterol-derived steroid.
The satiety hormone leptin is produced mainly by:
Leptin is secreted by adipocytes in proportion to fat mass and signals the hypothalamus to reduce appetite. Ghrelin, not leptin, is the main gastric appetite hormone.
A young woman presents with goitre, bulging eyes, heat intolerance and fine hand tremor. Which disorder is most likely?
These features suggest Graves disease; excess thyroid hormone raises metabolism, causing heat intolerance and tremor, while autoimmune orbitopathy causes exophthalmos. Labs show low TSH, high free T4.
Which effect is NOT caused by thyroid hormones?
Thyroid hormones raise the metabolic rate, so substrate use increases. They also increase heat production, heart rate and cardiac output, widening pulse pressure.
Which hormone acts on enterocytes to increase absorption of dietary calcium?
Calcitriol, the active vitamin D formed in the kidney, increases calcium-binding proteins in the gut lining. Calcitonin lowers blood calcium and has no role in absorption.
Cortisol and aldosterone are mainly inactivated and conjugated for excretion in which organ?
The liver reduces and conjugates steroid hormones (mainly with glucuronide), making them water-soluble; the kidneys then excrete the conjugates in urine.