The hormone 'Gastrin' acts on the gastric glands to stimulate the secretion of:
- Bile
- Hydrochloric acid
- Bicarbonate
- Insulin
Explanation: Gastrin stimulates the secretion of HCl and pepsinogen in the stomach to aid digestion.
The adrenal cortex is divided into three layers. Which is the outermost layer?
- Zona fasciculata
- Zona medullaris
- Zona reticularis
- Zona glomerulosa
Explanation: The order from outer to inner is: Zona glomerulosa (outer), Zona fasciculata (middle), and Zona reticularis (inner).
Glucocorticoids, particularly cortisol, are primarily involved in which metabolic process?
- Iodine uptake
- Carbohydrate metabolism
- Fat storage
- Water balance
Explanation: Glucocorticoids stimulate gluconeogenesis, lipolysis, and proteolysis to maintain glucose levels.
In males, which hormone stimulates the Leydig cells to produce androgens?
Explanation: Luteinizing Hormone (LH) in males is also called Interstitial Cell Stimulating Hormone (ICSH) because it acts on Leydig cells.
Hyperthyroidism resulting in protrusion of eyeballs and increased BMR is known as:
- Simple goitre
- Addison's disease
- Diabetes Mellitus
- Graves' disease
Explanation: Exophthalmic goitre (Graves' disease) is a form of hyperthyroidism characterized by eyeball protrusion and high BMR.
Which of the following acts as a 'second messenger' in the mechanism of hormone action?
Explanation: Hormones that interact with membrane-bound receptors generate second messengers like cAMP, $IP_3$, or $Ca^{++}$.
The hormone 'Vasopressin' primarily acts on which part of the nephron?
- Loop of Henle
- Distal tubule
- Glomerulus
- Proximal tubule
Explanation: Vasopressin (ADH) stimulates water and electrolyte resorption mainly from the distal convoluted tubules and collecting ducts.
The hormone 'Epinephrine' causes an increase in which of the following during stress?
- Glycogen synthesis
- Blood glucose
- Digestive activity
- Urine output
Explanation: Adrenaline stimulates the breakdown of glycogen into glucose, increasing the blood sugar level for energy.
Among the primary gastrointestinal hormones, which of the following specifically functions to inhibit gastric secretion and gastric motility?
- Gastric Inhibitory Peptide (GIP)
- Cholecystokinin (CCK)
- Secretin
- Gastrin
Explanation: Gastric Inhibitory Peptide (GIP) functions primarily to inhibit gastric secretion and movement, effectively slowing down the digestive process to allow for adequate absorption.
Which endocrine gland undergoes atrophy (shrinks) as a person reaches old age?
- Pituitary
- Thyroid
- Adrenal
- Thymus
Explanation: The thymus is large at birth but gradually degenerates with age, leading to a weaker immune response in elderly people.
Which specific hormone is responsible for the 'reddish' pigmentation of the skin in many animals?
Explanation: Melanocyte Stimulating Hormone (MSH) acts on melanocytes to regulate skin pigmentation.
The deficiency of adrenal cortex hormones can lead to which of the following diseases?
- Acromegaly
- Addison's disease
- Graves' disease
- Diabetes Insipidus
Explanation: Underproduction of hormones by the adrenal cortex alters carbohydrate metabolism, causing acute weakness (Addison's disease).
Which hormone is responsible for the 'Milk Ejection' reflex during breastfeeding?
- Oxytocin
- Estrogen
- Progesterone
- Prolactin
Explanation: While prolactin stimulates milk production, oxytocin stimulates the contraction of mammary muscles to eject milk.
Lipid-soluble hormones, like steroids, usually regulate gene expression by interacting with:
- Surface enzymes
- Second messengers
- Membrane receptors
- Intracellular receptors
Explanation: Steroid hormones cross the cell membrane and bind to receptors in the cytoplasm or nucleus to influence DNA transcription.
Which condition is caused by the hypersecretion of Growth Hormone in adults?
- Myxedema
- Gigantism
- Acromegaly
- Cretinism
Explanation: Excess growth hormone in adults leads to acromegaly (disfigured face/limbs). Gigantism occurs if hypersecretion happens during childhood.
The hormone 'Aldosterone' acts mainly at the renal tubules to promote the resorption of:
- Hydrogen ions
- Potassium ions
- Phosphate ions
- Sodium ions
Explanation: Aldosterone (a mineralocorticoid) stimulates the resorption of $Na^+$ and water, and the excretion of $K^+$.
Hormones that bind to membrane-bound receptors do not enter the cell but generate:
- Nuclear receptors
- Gene products
- Second messengers
- Primary messengers
Explanation: Peptide hormones trigger cellular responses by producing second messengers like cAMP, $IP_3$, or calcium ions.
Which gland plays a major role in the differentiation of T-lymphocytes for cell-mediated immunity?
- Thymus
- Thyroid
- Spleen
- Pancreas
Explanation: The thymus secretes thymosins, which are essential for the maturation of T-cells and immune response.
Hyperparathyroidism can lead to which skeletal issue?
- Muscle atrophy
- Demineralization
- Joint fusion
- Bone thickening
Explanation: Excess PTH causes too much calcium to be pulled from the bones, leading to weakened bones and potential fractures.
Glucagon stimulates which process in the liver to increase blood sugar?
- Protein synthesis
- Glycogenesis
- Glycogenolysis
- Lipogenesis
Explanation: Glucagon triggers the breakdown of glycogen into glucose (glycogenolysis) and promotes gluconeogenesis.
Which hormone is primarily responsible for the maintenance of pregnancy?
- Progesterone
- Estrogen
- LH
- FSH
Explanation: Progesterone supports pregnancy and acts on mammary glands to stimulate the formation of alveoli.
Prolonged 'Hyperglycemia' is a clinical hallmark of which endocrine disorder?
- Diabetes Mellitus
- Simple Goitre
- Addison's disease
- Diabetes Insipidus
Explanation: Diabetes Mellitus is characterized by persistently high blood sugar levels, often leading to glucose loss in urine.
Hormones are scientifically defined as non-nutrient chemicals that act as:
- Intercellular messengers
- Energy sources
- Structural proteins
- Catalytic enzymes
Explanation: Hormones are chemical messengers produced in trace amounts that carry signals between cells to regulate physiological processes.
The protein hormone 'Thyrocalcitonin' (TCT) performs which of the following functions?
- Stimulates BMR
- Regulates iodine
- Lowers calcium
- Raises calcium
Explanation: Thyrocalcitonin is a thyroid hormone that regulates blood calcium levels by lowering them.
Which hormone acts with androgens to regulate spermatogenesis in the testes?
- LH
- FSH
- Somatostatin
- Oxytocin
Explanation: Follicle Stimulating Hormone (FSH) and androgens are both required for the normal process of sperm production (spermatogenesis).
The hormone 'Testosterone' is produced by which specific cells in the testes?
- Stem cells
- Leydig cells
- Sertoli cells
- Spermatogonia
Explanation: Leydig cells (interstitial cells) produce a group of hormones called androgens, mainly testosterone.
The 'Melatonin' hormone, which regulates the 24-hour diurnal rhythm, is secreted by:
- Thymus
- Thyroid
- Pineal gland
- Adrenal medulla
Explanation: The pineal gland secretes melatonin, which helps maintain sleep-wake cycles and body temperature.
Which hormone released by the hypothalamus inhibits the release of Growth Hormone?
- Somatotropin
- Oxytocin
- Somatostatin
- Vasopressin
Explanation: Somatostatin from the hypothalamus inhibits the release of growth hormone (somatotropin) from the pituitary gland.
The hormone 'Secretin' acts on the exocrine pancreas to stimulate the secretion of:
- Bile juice
- Insulin
- Digestive enzymes
- Water and bicarbonate
Explanation: Secretin is a GI hormone that stimulates the secretion of water and bicarbonate ions from the pancreas.
Hypothyroidism during pregnancy can cause 'Cretinism' in the baby, characterized by:
- Protruding eyes
- Stunted growth
- High IQ
- Increased BMR
Explanation: Cretinism involves mental retardation, low intelligence quotient, abnormal skin, and stunted physical growth due to thyroid deficiency.
The hormone Prolactin is primarily involved in which of the following processes?
- Milk production
- Blood pressure
- Uterine contraction
- Water resorption
Explanation: Prolactin regulates the growth of mammary glands and the formation of milk in them.
Which hormone produced by the adrenal cortex suppresses the immune response?
- Aldosterone
- Adrenaline
- Testosterone
- Cortisol
Explanation: Cortisol produces anti-inflammatory reactions and is used medically to suppress immune responses during organ transplants.
The 'Neurohypophysis' of the pituitary gland is primarily responsible for storing:
- Oxytocin
- Insulin
- Growth hormone
- Prolactin
Explanation: The posterior pituitary (neurohypophysis) stores and releases oxytocin and vasopressin, which are actually synthesized by the hypothalamus.
The presence of 'Ketone bodies' in urine is a diagnostic indicator of:
- Thyroid failure
- Pituitary dwarfism
- Diabetes Mellitus
- Adrenal insufficiency
Explanation: When glucose cannot be used, the body breaks down fats excessively, producing ketone bodies that appear in the urine.
Thyroid hormones are essential for the maintenance of which physiological parameter?
- Basal metabolic rate
- Muscle mass
- Urine concentration
- Blood glucose
Explanation: Thyroid hormones (T3 and T4) play a critical role in regulating the body's BMR and protein/fat metabolism.
Hormones like Cortisol and Testosterone belong to which chemical category?
- Peptides
- Iodothyronines
- Amino-derivatives
- Steroids
Explanation: Steroid hormones include cortisol, testosterone, estradiol, and progesterone.
Which mineral is essential for the normal rate of hormone synthesis in the thyroid?
- Iron
- Iodine
- Magnesium
- Calcium
Explanation: Iodine is critical for the synthesis of thyroid hormones (T3 and T4). Deficiency leads to goitre.
Cholecystokinin (CCK) acts on which two organs to aid digestion?
- Pancreas and Gallbladder
- Stomach and Liver
- Kidney and Heart
- Thyroid and Thymus
Explanation: CCK stimulates the release of pancreatic enzymes and the contraction of the gallbladder to release bile.
A deficiency of ADH (Vasopressin) leads to the excretion of large amounts of dilute urine, known as:
- Uremia
- Diabetes Mellitus
- Glycosuria
- Diabetes Insipidus
Explanation: Diabetes Insipidus is caused by the failure of the posterior pituitary to release enough ADH, leading to excessive water loss.
Parathyroid hormone (PTH) increases blood calcium levels by acting on:
- Liver
- Bones
- Muscles
- Brain
Explanation: PTH stimulates bone resorption (dissolution/demineralization) to increase calcium levels in the blood.
Which hormone is secreted by the 'Corpus luteum' after ovulation?
- FSH
- Progesterone
- LH
- Estrogen
Explanation: The ruptured follicle transforms into the corpus luteum, which primarily secretes progesterone to support the uterine lining.
Which system transports hypothalamic hormones to the anterior pituitary gland?
- Cerebrospinal fluid
- Lymphatic system
- Arterial system
- Portal circulatory system
Explanation: The hypothalamic-hypophyseal portal system allows hypothalamic regulatory hormones to reach the anterior pituitary directly and rapidly.
In humans, the 'Pars intermedia' is almost merged with which pituitary part?
- Pars nervosa
- Pineal gland
- Hypothalamus
- Pars distalis
Explanation: In the human pituitary, the pars intermedia (which secretes MSH) is almost inseparable from the pars distalis (anterior pituitary).
Which pituitary hormone stimulates the synthesis and secretion of steroid hormones from the adrenal cortex?
Explanation: Adrenocorticotropic hormone (ACTH) stimulates the adrenal cortex to produce glucocorticoids.
Regarding calcium balance, which of the following pairs is functionally antagonistic?
- PTH and TCT
- LH and FSH
- Insulin and Glucagon
- Epinephrine and Cortisol
Explanation: Parathyroid Hormone (PTH) increases blood calcium, while Thyrocalcitonin (TCT) lowers it, maintaining calcium homeostasis.
The interaction of a hormone with its specific receptor leads to the formation of a/an:
- Enzyme-substrate complex
- Second messenger
- Hormone-receptor complex
- Protein kinase
Explanation: Each hormone binds to its specific receptor to form a complex (HRC), which then triggers biochemical changes in the target tissue.
Which hormone produced by the juxtaglomerular cells of the kidney stimulates erythropoiesis?
- Erythropoietin
- Angiotensin
- Calcitriol
- Renin
Explanation: Erythropoietin stimulates the formation of red blood cells (erythropoiesis) in the bone marrow.
The 'Catecholamines' (Adrenaline and Noradrenaline) are secreted by the:
- Adrenal medulla
- Adrenal cortex
- Thyroid follicles
- Islets
Explanation: The adrenal medulla secretes adrenaline (epinephrine) and noradrenaline, known as emergency hormones.
Which specific region of the brain is known as the 'master' of the master gland?
- Cerebrum
- Cerebellum
- Thalamus
- Hypothalamus
Explanation: The hypothalamus contains nuclei that produce hormones regulating the synthesis and secretion of pituitary hormones.
Where are the receptors for steroid hormones typically located within the target cell?
- Mitochondria
- Intracellular
- Cell membrane
- Extracellular
Explanation: Steroid hormones are lipid-soluble and diffuse into the cell to bind with intracellular (mostly nuclear) receptors.
Insulin acts on hepatocytes and adipocytes to achieve which effect?
- Increase glucose
- Decrease glucose
- Inhibit protein
- Break glycogen
Explanation: Insulin enhances cellular glucose uptake and utilization, resulting in a decrease in blood glucose levels.
The 'Atrial Natriuretic Factor' (ANF), which decreases blood pressure, is secreted by:
- Lungs
- Kidneys
- Liver
- Heart
Explanation: ANF is a peptide hormone secreted by the atrial wall of the heart when blood pressure increases.
The parathyroid glands are located on the 'posterior' side of the:
- Thyroid gland
- Adrenal gland
- Pancreas
- Thymus
Explanation: There are four parathyroid glands, one pair each in the two lobes of the thyroid gland on its back side.
Hypothyroidism in adult women can lead to which significant physiological change?
- Increased alertness
- Weight loss
- Irregular menstruation
- Early puberty
Explanation: Hypothyroidism often causes menstrual cycle irregularities and can lead to fertility issues in adult females.
Which hormone is critical for 'basal' levels of glucose in the blood between meals?
- Thyroxine
- Calcitonin
- Glucagon
- Insulin
Explanation: Glucagon is the primary 'fasting' hormone that prevents blood sugar from dropping too low by releasing glucose from the liver.
Hormones like Epinephrine and Norepinephrine are derived from which amino acid?
- Valine
- Tryptophan
- Methionine
- Tyrosine
Explanation: Catecholamines are amino-acid derivatives synthesized from the precursor tyrosine.
How many parathyroid glands are typically present in a human?
Explanation: Humans normally have four parathyroid glands located on the back side of the thyroid gland.
In the 'Islets of Langerhans', the $\alpha$-cells are responsible for secreting:
- Gastrin
- Glucagon
- Insulin
- Somatostatin
Explanation: $\alpha$-cells produce glucagon (hyperglycemic), while $\beta$-cells produce insulin (hypoglycemic).
The hormone 'Melatonin' influences which of the following in addition to sleep?
- Bone density
- Pigmentation
- Muscle strength
- Iodine levels
Explanation: Melatonin also influences pigmentation, the menstrual cycle, and our defense capability (immune system).
The hormone 'Estrogen' is primarily produced and secreted by:
- Pituitary gland
- Uterine wall
- Corpus luteum
- Growing ovarian follicles
Explanation: Estrogen is synthesized by the developing follicles in the ovary, while progesterone comes from the corpus luteum.