Endocrine and reproduction Flashcards
What are the male equivalents of the mullerian ducts in females?
Wolffian ducts
Can the Y and X chromosomes cross-over?
Yes, but only within a short pairing region
Can the Y chromosome cross over with the X chromosome at any point along its length?
No, the pairing region is comparatively short
What is the significance of thesrygene? Is it in the pairing region of the Y chromosome?
It is the sex determining region of the Y chromosome; no, it is in the non-pairing region (otherwise it could be transferred to X chromosomes!)
If the SRY gene is deleted or mutant in an otherwise normal XY male, what will the primordial gonads differentiate into?
Ovaries
What sex phenotype can result if the srygene is transferred to an X chromosome?
An XX male
What is the difference between genetic and gonadal sex?
Genetic is the configuration of X or Y chromosomes; gonadal is the presentation of a sex phenotype with formation of testes or ovaries
What do fetal testes synthesize that oppose the formation of the Mullerian duct system? Is it secreted by fetal ovaries? What hormone supports formation of the Wolffian duct system instead?
AMH, anti mullerian hormone; no, AMH is not secreted by ovaries; testosterone supports formation of the Wolffian duct system
Which week of embryonic development is when the penis and scrotum differentiate?
Weeks 9-10
What hormone is created from testosterone using5α reductase that allows for differentation of the male external genitalia?
Dihydrotestosterone (DHT)
If there is no SRY gene, will the ovaries secrete AMH, testosterone, or produce DHT?
No to all
By what week of embryonic development is the fetus fully differentiated into a male?
week 12
What causes testicular feminization?
A defect in androgen receptors: the duct system is insensitive to androgens
In androgen insensitivity disorder, do the uterus and fallopian tubes form? Do female external genitalia form?
No uterus of fallopian tubes, because AMH will still be released and effectively repress Mullerian duct formation; external female genitalia because testosterone and DHT cannot perform their actions
What disease causes masculinization of female external genitalia at birth?
Congenital adrenal hyperplasia
How does congenital adrenal hyperplasia cause masculinization of external genitalia?
Androgens are secreted by a hyperplastic adrenal gland
What enzyme defect in the adrenal gland can cause increased androgen production? What sex phenotype disorder does this cause?
21 hydroxylase deficiency; congenital adrenal hyperplasia
What sex phenotype disorder is this representative of?
Congenital adrenal hyperplasia
What is the median age for puberty onset in American females? What about in American males?
10 years for females; 12 years in males
What hormone is released in pulses of increased frequency and amplitude to initiate puberty?
GnRH
Do levels of LH periodically cycle before a girl reaches her reproductive years? What hormone besides LH is elevated during puberty?
No; FSH is also elevated during puberty
Of the pM, nM, μM and mM concentration ranges, which are most common for hormones?
pM and nM
In what two tissues are the enzymes related to steroid synthesis most prevalently expressed?
Adrenal cortex, gonads
Phosopholipase C, when activated by active α G-protein, performs what action on PIP2? What effect does this have on Ca++cytosolic concentration, and how?
It cleaves it to form diacylglycerol (DAG) and IP3; IP3goes on to open calcium channels and increase cytosolic Ca++
The anterior pituitary arises from an evagination of what pouch?
Rathke’s pouch
What is the shortest hypothalamic peptide hormone?
TRH, with three amino acids
For each hormone(s), name the cell type in the pituitary that produces it.– ACTH– LH and FSH– TSH– PRL– GH
– ACTH: corticotroph– LH and FSH: gonadotroph– TSH: thyrotroph– PRL: lactotroph– GH: somatotroph
For each of the following pituitary cell types, name the hormone(s) that they release.– corticotroph– gonadotroph– thyrotroph– lactotroph– somatotroph
– corticotroph: ACTH– gonadotroph: LH & FSH– thyrotroph: TSH– lactotroph: PRL– somatotroph: GH
Hypothalamically secreted hormones acting via Gsproteins include[…], GnRH, ADH, GHRH, and oxytocin.
Hypothalamically secreted hormones acting via Gsproteins includeTRH, GnRH, ADH, GHRH, and oxytocin.
Hypothalamically secreted hormones acting via Gsproteins includeTRH, […], ADH, GHRH, and oxytocin.
Hypothalamically secreted hormones acting via Gsproteins includeTRH, GnRH, ADH, GHRH, and oxytocin.
Hypothalamically secreted hormones acting via Gsproteins includeTRH, GnRH, […], GHRH, and oxytocin.
Hypothalamically secreted hormones acting via Gsproteins includeTRH, GnRH, ADH, GHRH, and oxytocin.
Hypothalamically secreted hormones acting via Gsproteins includeTRH, GnRH, ADH, […], and oxytocin.
Hypothalamically secreted hormones acting via Gsproteins includeTRH, GnRH, ADH, GHRH, and oxytocin.
Hypothalamically secreted hormones acting via Gsproteins includeTRH, GnRH, ADH, GHRH, and […].
Hypothalamically secreted hormones acting via Gsproteins includeTRH, GnRH, ADH, GHRH, and oxytocin.
Can serum amino acids stimulate GH release?
Yes
Are growth hormone receptors found only in the liver or throughout the body? What signalling protein is thought to faciitate indirect effects of GH?
Throughout the body; IGF-1, also called somatomedin
What is the standard treatment for growth hormone deficiency? Can a patient with Laron dwarfism be treated with it as well?
Growth hormone supplementation; no, because Laron dwarfism involves a receptor mutation
Which receptor does somatomedin act at? Is it a potential treatment for Laron dwarfism? Why or why not?
It acts at IGF (the insulin receptor); it is a potential treatment for Laron dwarfism; this is because it acts at a different receptor than the one mutated in Laron dwarfism (GH receptor)
Is the predominant regulation of prolactin via stimulated secretion or inhibition of primary tone?
Inhibition of primary tone
What neurotransmitter is prolactin inhibiting hormone chemically equivalent to?
Dopamine
What signal transduction pathway does prolactin’s receptor use?
Jak-Stat
What accounts for ~70% of pituitary tumors? What is the most common clinical feature that presentsspecifically?
Prolactinomas; galactorrhea (spontaneous discharge from mammary gland)
How are prolactinomas treated?
Dopamine agonists (bromocriptine, cabergoline)
In the pituitary-thyroid axis, what hormone is secreted by the hypothalamus? The anterior pituitary? The thyroid gland?
hypothalamus: TRH; anterior pituitary: TSH; thyroid: thyroid hormones
What two sets of nuclei contain hypothalamic neurons that release hormones into the posterior pituitary?
Paraventricular nuclei and supraoptic nuclei
What downregulates TRH receptors of thyrotropes? Where are thyrotropes found?
High intracellular T3; thyrotropes are in the anterior pituitary
What is TRH’s effect on prolactin? What is primary hypothyroidism’s effect on prolactin?
TRH positively regulates prolactin; therefore, primary hypothyroidism, where TRH is high, would associate with hyperprolactinemia
How many transmembrane domains are in a GPCR?
7
The α subunit of TSH shares homology with what three other peptide hormones?
FSH, LH, and hCG
What negatively regulates TSH secretion?
T3and T4
What type of receptor is the TSH receptor?
GPCR
What cotransport efficiently concentrates I-ion within thyroid cells? What enzyme catalyzes oxidation to I2?
Na+/I-cotransport; thyroid peroxidase
Which amino acids of thyroglobulin are substrates for iodine incorporation? At how many sites can iodine be incorporated?
Tyrosine; one or two
What hormone stimulates endocytosis of thyroglobulin into the follicular cells of the thyroid?
TSH
What two drugs competitively inhibit Na+/I-cotransport? What two drugs can inhibit thyroid peroxidase (TPO) activity?
Thiocyanate and perchlorate inhibit Na+/I-cotransport; methimazole and propylthiouracil (PTU) inhibit TPO activity
Is most T3and T4in serum protein-bound?
Yes, normally 99%
What enzymes can convert T4to T3or rT3?
Deiodinases
What does the number in T3or T4signify?
The number of iodine residues
Where does the thyroid receptor reside within cells? When it is bound to T3, what does it function as? Can T4bind with as great affinity?
It is nuclear; it acts as a transcription factor when active; T3binds with 10x greater affinity than T4
Where is the thyroid receptor expressed? What is the effect of thyroid hormone on O2consumption, basal metabolic rate, body temperature, synthesis of Na+/K+ATPase?
Essentially ubiquitously; all of these increase
Does thyroid hormone increase cardiac output via increased heart rate, contractility, both, or neither?
Both
What hormone(s) act in conjunction with growth hormone to promote growth?
Thyroid hormones
Is calcitonin secreted by the thyroid or the parathyroid? Which cell type secretes it?
Thyroid; C cells that are parafollicular
Is parathyroid hormone or calcitonin the primary modulator of blood Ca++?
Parathyroid hormone is primary
Is TSH elevated or low in primary hypothyroidism? What about secondary hypothyroidism?
Elevated in primary hypothyroidism, low in secondary hypothyroidism
For each of the following symptoms, would hypothyroidism or hyperthyroidism be a more likely cause?– decrease in metabolic rate– loose stools– jitteriness and tremor– tachycardia– cold intolerance and dry skin– poor linear growth as a child
– decrease in metabolic rate: hypo– loose stools: hyper– jitteriness and tremor: hyper– tachycardia: hyper– cold intolerance and dry skin: hypo– poor linear growth as a child: hypo
What is the most common etiology of primary hypothyroidism? What causes it?
Hashimoto’s thyroiditis; autoimmune destruction of the thyroid gland
Defects in the TSH receptor, Na+/I-cotransport, thyroglobulin, and thyroid peroxidase can cause what endocrine disorder?
Congenital hypothyroidism
What endocrine disorder is depicted here?
Congenital hypothyroidism
What dietary condition causes hypothyroidism?
Iodine deficiency
What is this patient, who presents with tachycardia and jitters, suffering from? What is its etiology?
Grave’s disease; production of auto-antibodies that stimulate the TSH receptor (mimicking TSH)
What causes the exophthalmos of Grave’s disease?
TSH acts at the fibroblasts of the eye muscles, it is not related to the high levels of thyroid hormones
What peptide hormone is most homologous to oxytocin?
ADH (vasopressin)
What are two types of receptors that provide input for vasopressin secretion?
Osmoreceptors in the hypothalamus and cardiac baroreceptors
Does angiotensin II stimulate or inhibit ADH release?
Stimulate
Does increased plasma volume increase or decrease ADH secretion? Does increased plasma osmolality increase or decrease ADH secretion?
Increased plasma volume (hypervolemia) → ADH↓Increased plasma osmolality → ADH↑
Where are the two types of vasopressin receptors located?
V1receptor: vascular smooth muscle;V2receptor: kidney
What intracellular signaller participates in the insertion of aquaporin channels into the distal tubule and collecting duct upon ADH stimulation?
cAMP
What are the two principal mechanisms for diabetes insipidus? What is the presenting symptom?
Vasopressin deficiency or vasopressin resistance; polyuria (high dilute urinary volume)
What test distinguishes between central or nephrogenic diabetes insipidus?
Water deprivation test: after water deprivation, let plasma osmolality rise to 295 mmol/kg and then administer ADH, if urine osmolality rises there is a central ADH deficiency, otherwise ADH resistance (nephrogenic)
What does SIADH stand for? What is the presenting serum test abnormality for SIADH?
Syndrome of Inappropriate ADH; severe hyponatremia
What receptor type is shared by the receptors for ADH and oxytocin?
They are all GPCRs
Which part of the adrenal gland synthesizes steroids? Which part synthesizes catecholamines?
Cortex: steroids; medulla: catecholamines
What hormones are produced by cleavage of POMC(pro-opiomelanocortin)?
MSH, endorphin, lipotrophin, and ACTH
What does ACTH stand for?
Adrenocorticotropic hormone
Are steroids produced in a pulsatile or steady manner? Does production go up, down, or stay the same at night?
Pulsatile; it goes down at night
What is the common metabolic precursor for steroid hormones?
Cholesterol
What are the two major classes of adrenal enzymes?
Cytochrome P450 oxidases and hydroxysteroid dehydrogenase
Do steroid hormone receptors reside in the nucleus or cytoplasm when inactive?
Cytoplasm
What is the difference between cortisol and prednisone?
The ratio between glucocorticoids and mineralocorticoids; prednisone has more glucocorticoids