199 Questions
What is the response to a decrease in serum Ca2+ concentration in the parathyroid gland?
Increased secretion of parathyroid hormone
What is the result of parathyroid hormone's actions on bone, kidney, and intestine?
Increased serum Ca2+ concentration
What happens to parathyroid hormone secretion when serum Ca2+ concentration increases?
Parathyroid hormone secretion decreases
Which hormone inhibits the secretion of prolactin?
Prolactin-inhibiting factor
What is a characteristic of positive feedback?
It is a self-reinforcing process
Which hormone is responsible for stimulating the secretion of TSH and prolactin?
Thyrotropin-releasing hormone
Which hormone stimulates the synthesis and secretion of thyroid hormones?
Thyroid-stimulating hormone
Which hormone promotes sperm maturation?
Follicle-stimulating hormone
Which hormone stimulates milk production and breast development?
Prolactin
Which hormone stimulates the reabsorption of water by renal collecting ducts?
Antidiuretic hormone
Which hormone stimulates the synthesis of melanin?
Melanocyte-stimulating hormone
What is the result of the surge of luteinizing hormone just before ovulation?
An increase in estrogen secretion by the ovaries
What is an example of down-regulation of receptors?
Progesterone down-regulating its own receptor and the receptor for estrogen in the uterus
What is the function of G proteins in hormone signaling?
To couple hormone receptors to adjacent effector molecules
What happens to a G protein when GTP is bound to its a subunit?
The G protein becomes active
What is the result of estrogen up-regulation of its own receptor in the ovary?
An increase in the sensitivity of the ovary to estrogen
What is a characteristic of G proteins?
They have intrinsic GTPase activity
What type of activity do catalytic receptors possess on the intracellular side of the membrane?
Enzymatic
What is the second messenger produced in response to atrial natriuretic peptide (ANP)?
cGMP
What is the function of phospholipase C in the IP3-Ca²⁺ signaling pathway?
Breaks down PIP₂ to produce IP₃ and DAG
Which type of receptor is associated with guanylyl cyclase activity?
Receptor guanylyl cyclase
What is the function of protein kinase C in the IP3-Ca²⁺ signaling pathway?
Phosphorylates and activates downstream targets
What type of receptor is associated with tyrosine kinase activity?
Tyrosine kinase receptors
What is the effect of a stimulatory G protein on adenylate cyclase?
It activates adenylate cyclase
What is the role of phosphodiesterase in the cAMP pathway?
It degrades cAMP to 5'-AMP
What is the result of IP3 mobilizing Ca2+ from the endoplasmic reticulum?
It activates protein kinase C
What is the role of the G protein in the IP3 mechanism?
It activates phospholipase C
What is the effect of an inhibitory G protein on adenylate cyclase?
It inhibits adenylate cyclase
What is the purpose of protein kinase A in the cAMP pathway?
It phosphorylates specific proteins
Which of the following hormones is synthesized from a different precursor than ACTH?
FSH
What is the role of GHRH in the regulation of growth hormone secretion?
Stimulates the synthesis and secretion of growth hormone
What is the effect of sleep on growth hormone secretion?
Increases growth hormone secretion
Which of the following is NOT a stimulator of growth hormone secretion?
Obesity
What is the structural characteristic shared by TSH, LH, and FSH?
They all have identical α subunits
What is the function of somatostatin in the regulation of growth hormone secretion?
Inhibits growth hormone synthesis and secretion
What is the result of the binding of steroid hormones to their receptors?
The hormone-receptor complex dimerizes and binds to DNA
What is the function of the hypothalamichypophysial portal system?
To deliver hormones from the hypothalamus to the pituitary gland
What is the origin of the posterior lobe of the pituitary gland?
Derived from neural tissue
What is the function of the nerve cell bodies in the posterior pituitary gland?
To synthesize and release hormones
What is the role of growth hormone and prolactin in the anterior pituitary gland?
They are discussed in detail in this section
What is the mechanism of action of steroid hormones?
They bind to receptors in the cytoplasm and regulate gene transcription
What is the primary mechanism by which prolactin inhibits its own secretion?
By stimulating the release of dopamine from the hypothalamus
What is the effect of hypothalamic destruction on prolactin secretion?
Increased prolactin secretion due to loss of tonic inhibitory control by dopamine
What is the effect of prolactin on ovulation?
It inhibits ovulation by decreasing GnRH release
What is the result of prolactin deficiency?
Failure to lactate due to decreased casein and lactalbumin synthesis
What is the effect of sleep on prolactin secretion?
It increases prolactin secretion due to increased TRH release
What is the role of estrogen in regulating prolactin secretion?
It stimulates prolactin secretion during pregnancy
What is the function of somatomedins in relation to growth hormone?
They inhibit the secretion of growth hormone by acting directly on the anterior pituitary.
How does growth hormone affect its own secretion?
It inhibits its own secretion by stimulating the secretion of somatostatin from the hypothalamus.
What is the effect of growth hormone on glucose uptake into cells?
It decreases glucose uptake into cells.
What is the receptor for insulin-like growth factors (IGFs) similar to?
The receptor for insulin.
What is the effect of growth hormone on protein synthesis in muscle?
It stimulates protein synthesis in muscle.
What is the role of GHRH in growth hormone secretion?
It stimulates the secretion of growth hormone from the anterior pituitary.
What is the primary function of antidiuretic hormone in the body?
To regulate the serum osmolarity by increasing the H2O permeability of the late distal tubules and collecting ducts
What is the mechanism of action of antidiuretic hormone in the principal cells of the late distal tubule and collecting duct?
Via a V2 receptor and an adenylate cyclase-cAMP mechanism
What is the effect of antidiuretic hormone on vascular smooth muscle?
Constriction of vascular smooth muscle
What is the effect of antidiuretic hormone on the thick ascending limb?
Increased Na+-2CI--K+ cotransport
What is the effect of antidiuretic hormone on the inner medullary collecting ducts?
Increased urea recycling
What is the primary site of origin of oxytocin in the hypothalamus?
Paraventricular nuclei
What is the mechanism by which TSH increases thyroid hormone secretion?
via an adenylate cyclase-cAMP mechanism
What is the effect of chronic elevation of TSH on the thyroid gland?
hypertrophy of the thyroid gland
What is the function of thyroid-stimulating immunoglobulins in patients with Graves disease?
they bind to TSH receptors and stimulate the thyroid gland to secrete T3 and T4
What is the role of T3 in growth attainment?
it acts synergistically with growth hormone and somatomedins to promote bone formation
What is the effect of T3 on TSH secretion?
it inhibits TSH secretion
What is the relative potency of T3 compared to T4?
T3 is three to four times more potent than T4
What is the form of 1- to 12 that is reactive and will be 'organified' by combination with tyrosine on thyroglobulin?
12
Which enzyme is inhibited by propylthiouracil, leading to a reduction in thyroid hormone synthesis?
Peroxidase
What is the effect of high levels of I- on the synthesis of thyroid hormones?
Inhibition of organification
What is the more active form of thyroid hormone synthesized in the thyroid gland?
T3
What is the result of the coupling of one molecule of DIT with one molecule of MIT?
Formation of T3
Where does the organification of 12 take place in the thyroid gland?
Junction of follicular cells and follicular lumen
What is the effect of high thyroid hormone levels on TSH levels?
Decreases TSH levels
What is the site of estrogen production?
Ovaries and placenta
What is the effect of low thyroid hormone levels on the anterior pituitary?
Increases TSH secretion
What is the function of propylthiouracil in the treatment of hyperthyroidism?
Inhibits the synthesis of thyroid hormone
What is the result of oxidizing the A ring in the production of estrogens?
Formation of estrogens
What is the consequence of thyroid hormone deficiency on bone age in relation to chronological age?
Bone age is less than chronological age
What is the primary role of thyroid hormone in the central nervous system during the perinatal period?
Maturation of the CNS
What is the effect of hyperthyroidism on the autonomic nervous system?
It increases sympathetic nervous system activity
What is the effect of thyroid hormone on basal metabolic rate (BMR) in most tissues?
It increases BMR
What is the consequence of hypothyroidism on mental function in adulthood?
It causes listlessness and impaired memory
What is the effect of thyroid hormone on Na+, K+-ATPase activity?
It increases Na+, K+-ATPase activity
What is the result of hydroxylation at C-17 in the production of steroids?
Production of glucocorticoids (cortisol)
What is the characteristic of 19-carbon steroids?
They have androgenic activity and are precursors to estrogens
What is the result of cleaving the C20,21 side chain in previously hydroxylated steroids?
Production of 19-carbon steroids, such as dehydroepiandrosterone or androstenedione
What is the characteristic of adrenal androgens?
They have a ketone group at C-17 and are excreted as 17-ketosteroids in the urine
What is the result of converting androstenedione in the testes?
Production of testosterone
What is the characteristic of hypothyroidism?
Decreased metabolic rate
What is a characteristic symptom of glucocorticoid deficiency?
Lack of pubic and axillary hair in women
What is the primary cause of Cushing syndrome?
All of the above
What is a characteristic feature of secondary adrenocortical insufficiency?
No hyperpigmentation
What is the effect of elevated cortisol levels?
Hyperglycemia
What is a characteristic of Cushing disease?
Overproduction of ACTH
What is the treatment for aldosterone-secreting tumors?
Surgical removal of the tumor
What is the primary mechanism by which aldosterone increases renal Na+ reabsorption?
By increasing the permeability of the distal tubule to sodium
What is the effect of angiotensin II on the adrenal cortex?
It increases the conversion of corticosterone to aldosterone
What is the effect of hyperkalemia on aldosterone secretion?
It increases aldosterone secretion
What is the primary mechanism by which glucocorticoids increase gluconeogenesis?
By increasing protein catabolism in muscle and decreasing protein synthesis
What is the effect of glucocorticoids on adipose tissue?
They decrease glucose utilization and insulin sensitivity
What is the effect of glucocorticoids on lipolysis?
They increase lipolysis and provide more glycerol to the liver for gluconeogenesis
Which of the following enzymes is involved in the synthesis of 17-hydroxyprogesterone?
17a-hydroxylase
What is the name of the hormone that stimulates the synthesis and secretion of ACTH from the anterior pituitary?
Corticotropin-releasing hormone (CRH)
What is the primary cause of Addison disease?
Autoimmune destruction of the adrenal cortex
What is the daily rhythm of cortisol secretion in individuals who sleep at night?
Highest in the morning and lowest in the evening
What is the effect of low cortisol levels on ACTH secretion?
Stimulates ACTH secretion by negative feedback
What is the second messenger involved in the signaling pathway of CRH?
cAMP
What is the characteristic of hyperpigmentation in Addison disease?
Caused by the stimulation of MSH by ACTH
What is the effect of aldosterone deficiency on the body?
Hyperkalemia and metabolic acidosis
Which zone of the adrenal cortex is responsible for the production of mineralocorticoids?
Zona glomerulosa
What is the characteristic of weight loss in Addison disease?
Caused by the deficiency of cortisol
What is the product of the enzyme 17,20-lyase?
Androstanedione
What is a common characteristic of Cushing disease?
All of the above
What is the effect of elevated cortisol levels on bone?
Increased bone resorption
What is the primary function of ketoconazola in treating Cushing disease?
Inhibiting steroid hormone synthesis
What is a characteristic of hyperaldosteronism-Conn syndrome?
Hypertension and hypokalemia
What is the most common biochemical abnormality of the steroidogenic pathway?
21-Hydroxylase deficiency
What happens to cortisol and aldosterone levels in 21-hydroxylase deficiency?
Both decrease
What is the primary effect of insulin binding to its receptor?
Increased phosphorylation of J3 subunits
Which of the following factors decreases insulin secretion?
Somatostatin
What is the effect of insulin on glucose uptake into target cells?
Increased glucose transporters are inserted into cell membranes
What is the result of insulin down-regulating its own receptors?
Decreased insulin sensitivity in target tissues
Which of the following hormones has an opposite effect on blood glucose levels compared to insulin?
Glucagon
What is the effect of starvation on insulin receptor levels?
Increased insulin receptor levels
What is the net effect on serum [Ca2+] in growing children?
It increases
What is the primary role of the C peptide in diabetic patients?
To monitor beta cell function
What is the effect of glucose on the beta cells?
Closing of K+ channels
Which hormone plays a major role in regulating serum [Ca2+]?
Parathyroid hormone (PTH)
What is the mechanism of action of sulfonylurea drugs on insulin secretion?
Closing of K+ channels
What happens to Ca2+ absorption in the intestine when vitamin D is activated?
It increases
What is the effect of PTH on the kidney?
It increases reabsorption of Ca2+
What is the structural characteristic of the insulin receptor?
Tetramer with two a subunits and two β subunits
What is the effect of calcitonin on bone?
It decreases bone resorption
What is the function of the β subunits of the insulin receptor?
Intrinsic tyrosine kinase activity
What is the result of depolarization of the beta cells?
Increase in intracellular [Ca2+] and secretion of insulin
What is the result of a negative Ca2+ balance in women during pregnancy or lactation?
Ca2+ is mobilized from the maternal bones
What is the effect of decreased serum magnesium levels on parathyroid hormone secretion?
Initially stimulates, then inhibits
What is the response to increased serum calcium levels in the parathyroid gland?
Inhibits PTH secretion
What is the mechanism by which decreased serum calcium levels stimulate PTH secretion?
Decreased binding to Ca2+-sensing receptors
What is the second messenger for PTH secretion by the parathyroid gland?
cAMP
What is the overall effect of PTH actions on its target tissues?
Increase in serum calcium and decrease in serum phosphate
What is the primary effect of insulin on glycogen metabolism?
Inhibition of glycogenolysis
What is the effect of insulin on blood fatty acid concentration?
Decreased blood fatty acid concentration
What is the effect of insulin on protein metabolism?
Stimulation of amino acid uptake and protein synthesis
What is the effect of insulin on blood K+ concentration?
Decreased blood K+ concentration
What is the underlying cause of hyperglycemia in the case study?
Insulin deficiency
What is the effect of insulin on phosphofructokinase activity?
Stimulation of phosphofructokinase activity
What is the effect of parathyroid hormone on phosphate reabsorption in the proximal tubule?
It decreases phosphate reabsorption
What is the effect of parathyroid hormone on the serum ionized [Ca2+]?
It increases the serum ionized [Ca2+]
What is the result of parathyroid hormone-mediated bone resorption on hydroxyproline excretion?
It increases hydroxyproline excretion
What is the effect of parathyroid hormone on urinary cAMP excretion?
It increases urinary cAMP excretion
What is the characteristic of primary hyperparathyroidism in terms of serum [Ca2+]?
It is characterized by hypercalcemia
What is the effect of parathyroid hormone on intestinal Ca2+ absorption?
It increases intestinal Ca2+ absorption indirectly
What is the primary cause of hypocalcemia in chronic renal failure?
Increased serum phosphate levels
What is the characteristic of pseudohypoparathyroidism type 1?
Defective G protein in the kidney and bone
What is the effect of furosemide on hypocalcemia?
It increases serum calcium levels
What is the function of Sa-reductase in the accessory sex organs?
To convert testosterone to dihydrotestosterone
What is the characteristic of familial hypocalciuric hypercalcemia (FHH)?
Decreased urinary Ca2+ excretion and increased serum Ca2+
What is the result of secondary hyperparathyroidism in chronic renal failure?
Increased bone resorption and osteomalacia
Which hormone stimulates the secretion of FSH and LH from the anterior pituitary?
GnRH
What is the effect of etidronate on hypocalcemia?
It inhibits bone resorption
What is the effect of inhibin on FSH secretion?
Negative feedback
Which cells do not contain 21-hydroxylase or 11-hydroxylase?
Leydig cells
What is the effect of LH on the Leydig cells?
Stimulation of testosterone synthesis
What is the function of finasteride in the treatment of benign prostatic hyperplasia?
Blockage of testosterone activation to dihydrotestosterone
What is the primary function of vitamin D in the body?
To increase intestinal calcium and phosphate absorption
What is the effect of decreased serum calcium levels on 1α-hydroxylase activity?
It increases the activity
Which of the following is an inactive form of vitamin D?
25-hydroxycholecalciferol
What is the role of vitamin D-dependent Ca2+-binding protein (calbindin D-28K) in the intestine?
It is involved in calcium absorption
What is the result of vitamin D deficiency in children?
Rickets
What is the effect of increased serum phosphate levels on 1α-hydroxylase activity?
It decreases the activity
What is the role of testosterone in the regulation of spermatogenesis?
It reinforces the spermatogenic effects of FSH in the Sertoli cells
Which hormone plays a crucial role in the regulation of male reproductive hormones?
GnRH
What is the site of testosterone synthesis?
Leydig cells
What is the effect of testosterone on the Sertoli cells?
It stimulates the production of inhibin
What is the enzyme responsible for the conversion of testosterone to dihydrotestosterone?
5-alpha-reductase
What is the effect of testosterone on the anterior pituitary?
Inhibition of LH secretion
What is the role of inhibin in the regulation of FSH secretion?
Inhibition of FSH secretion
What is the effect of dihydrotestosterone on target tissues?
Differentiation of penis, scrotum, and prostate
What is the effect of GnRH on the anterior pituitary?
Stimulates the secretion of FSH and LH
What is the function of 17β-hydroxysteroid dehydrogenase in the granulosa cells?
Converts testosterone to 17β-estradiol
What is the characteristic of androgen insensitivity disorder?
Deficiency of androgen receptors in target tissues
What initiates puberty in males and females?
Onset of pulsatile GnRH release from the hypothalamus
What is the pattern of FSH and LH levels in childhood?
FSH > LH
What is the source of androstenedione in the ovary?
Theca cells
What is the result of lack of testosterone receptors in the anterior pituitary?
Increased testosterone levels due to lack of feedback inhibition
What is the pattern of FSH and LH levels in senescence?
FSH > LH
What is the function of LH in the ovary?
Stimulates the synthesis of androstenedione
What is the effect of inhibin on the anterior pituitary?
Inhibits the secretion of FSH
What is the effect of testosterone on the epididymis?
Differentiates the epididymis
What is the characteristic of androgen insensitivity disorder?
Deficiency of androgen receptors in target tissues
What is the effect of dihydrotestosterone on the prostate?
Stimulates the growth of prostate
What is the primary source of estrogen in the ovary?
Granulosa cells
What is the effect of testosterone on the anterior pituitary?
Inhibits the secretion of LH
What stimulates the conversion of androstenedione to testosterone in the ovary?
17β-hydroxysteroid dehydrogenase
What is the trigger for the onset of puberty in males?
The pulsatile release of GnRH from the hypothalamus
What is the pattern of FSH and LH levels in childhood?
FSH > LH
What is the effect of GnRH on its own receptor in the anterior pituitary?
Up-regulation
What is the direction of diffusion of androstenedione in the ovary?
From theca cells to granulosa cells
What is the pattern of FSH and LH levels in senescence?
FSH > LH
This quiz covers the role of parathyroid hormone in regulating serum calcium levels, its secretion and feedback mechanisms.
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