(M) Lec 1: Introduction to Endocrinology Flashcards by Kchianna Lauren Coronel

A network of ductless glands that secrete hormones
The regulatory system of the body (for the control of different body functions)

Endocrine System

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Chemical signals that regulate or control the activities of the body by being transported from one cell to another

Hormones

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Types of Hormone Actions

Trasmitted/secreted via the bloodstream

Endocrine Hormones

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Types of Hormone Actions

Transmitted via the GIT

Exocrine Hormones

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Types of Hormone Actions

Transmitted via the neurons (neurologically-transmitted hormones)

Neurocrine

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Types of Hormone Actions

Transmitted through the interstitial fluid

Paracrine Hormones

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Other Types of Hormone Actions

Binds to specific receptors on the cell of origin resulting to self-regulation of its function

Autocrine

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Other Types of Hormone Actions

Acts on adjacent cells by direct cell-to-cell contact

Juxtacrine

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Other Types of Hormone Actions

Remains inside the synthesis of origin

Intracrine

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Feedback Mechanisms

↑ Hormone = ↑ Activity and Production Rate

Positive Feedback Mechanism

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Feedback Mechanisms

The LH and FSH are responsible for stimulating what organs?

Gonads (testis and ovaries)

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Feedback Mechanisms

What sex hormones do the testes and ovaries secrete (3)?

Testosterone (testis)
Estradiol and Progesterone (ovaries)

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Feedback Mechanisms

↑ Hormone = ↓ Activity and Production Rate

Negative Feedback Mechanism

Note: The signal is sent to the hypothalamus to stop the production of GnRH, LH, FSH, and sex hormones

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Classification of Hormones

Are hydrophilic (water-soluble); they cannot cross the cell membrane therefore it only takes effect on the surface of cells
e.g. Glycoproteins and Polypeptides

Peptides and Proteins

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Classification of Hormones

Glycoproteins or Polypeptides?
- FSH, HCG, TSH, Erythropoietin

Glycoproteins

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Classification of Hormones

Glycoproteins or Polypeptides?
- ACTH, ADH, GH, angiotensin, calcitonin, cholecystokinin, gastrin, glucagon, insulin, melanocyte-stimulating hormone, oxytocin, prolactin, and somatostatin

Polypeptides

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Classification of Hormones

Are hydrophobic/water-insoluble
Produced by the adrenal glands, ovaries, testes, and placenta
e.g. aldosterone, cortisol, estradiol, progesterone, testosterone, and activated vitamin D

Steroids

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Classification of Hormones

Derived from amino acids and are intermediary between (composed of) steroids and proteins
Some parts are hydrophilic while some are hydrophobic
e.g. epinephrine, norepinephrine, T3, and T4

Amines

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Endocrine Glands

A link between the nervous system and endocrine system
Serves as the “master” to the master gland (pituitary gland; secretes hormones that activate other glands)
This secretes “releasing hormones” while the pituitary secretes “stimulating hormones”

Hypothalamus

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Endocrine Glands

Where are ADH and Oxytocin specifically produced and synthesized within the hypothalamus (2)?

ADH - supraoptic nuclei
Oxytocin - paraventricular nuclei

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Endocrine Glands

It is a common misconception that ADH and Oxytocin are produced in the posterior pituitary gland when in fact it is produced in the hypothalamus. How did the misconception come to be?

Since the hypothalamus is connected to the posterior pituitary gland, its actual role is the FACILITATION OF RELEASE of ADH and oxytocin

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Endocrine Glands

The ff. hormones are classified as what (according to their place of synthesis)?
- Thyrotropin-relasing hormones (TRH), GnRH, Somatostatin (GR-IH), Growth hormone releasing hormone (GH-RH), and Prolactin-inhibiting factor (PIF)

Hypophyseal Hormones

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Endocrine Glands

Thyrotropin-relasing hormones (TRH) are capable of activating what gland?

Anterior Pituitary Gland

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Endocrine Glands

Upon the activation of the anterior pituitary gland, what hormones get secreted to be released to the thyroid?

Thyroid-stimulating Hormone (TSH)

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# Endocrine Glands Upon the activation of the thyroid gland by TSH, what hormones get produced (2)?

T3 and T4

# Endocrine Glands - Responsible for the secretion of melatonin which is important for the decrease of skin pigmentation - The secretion of melatonin is controlled by nerve stimuli

Pineal Gland

# Endocrine Glands - Aka hypophysis or the Master Gland - Hormones are regulated by hypothalamic secretions - Has an anterior and posterior portion

Pituitary Gland

# Endocrine Glands The anterior and posterior pituitary glands are also known as? (2)

1. Anterior - adenohypophysis (the true endocrine gland) 2. Posterior - neurohypophysis

# Endocrine Glands TOF: The posterior pituitary gland produces ADH and Oxytocin

False (it is merely released; it is produced in the hypothalamus)

# 5 Types of Cells in the Anterior Pituitary Gland An example is the growth hormone

Somatotrophs

# 5 Types of Cells in the Anterior Pituitary Gland An example is prolactin

Lactotrophs

# 5 Types of Cells in the Anterior Pituitary Gland An example is TSH

Thyrotrophs

# 5 Types of Cells in the Anterior Pituitary Gland Examples are FSH and LH

Gonadotrophs

# 5 Types of Cells in the Anterior Pituitary Gland An example is proprioomelanocortin (POMC) which is later on converted to ACTH, beta-endorphin, and beta-lipotropin

Corticotrophs

# Hormones of the Anterior Pitutary - Structurally similar to prolactin and human placental lactogen - Is controlled by GH-RH and GH-IH (somatostatin) produced by the hypothalamus - Its overall metabolic effect is to metabolize fat stores while conserving glucose

Growth Hormone

# Growth Hormone Increases or Supresses GH? 1. Hypoglycemia 2. Hyperglycemia

1. Increases GH (to conserve glucose) 2. Supresses GH (to reduce glucose)

# Growth Hormone Insulin-like Growth Factor 1 is also known as?

Somatomedin

# Growth Hormone This is an important stimulator for the secretion of GH

Ghrelin

# Growth Hormone What is the major stimulant of the growth hormone?

Sleep

# Growth Hormone Deficiency - The most common cause of dwarfism in children - Aka true dwarfism/pituitary dwarfism; there is a problem with the anterior pituitary

Idiopathic Growth Hormone Disorder

# Growth Hormone Deficiency The ff. types of dwarfism involve the dysfunction of what? - Laron dwarfism and African pygmy dwarfism - Prevents the production of somatomedin by the liver

Growth Hormone Receptors

# Growth Hormone Deficiency An excess of this leads to dwarfism as this has anti-GH activity

Glucocorticoids

# Growth Hormone Deficiency In this condition, hypothyroidism is evident (decreased T3 and T4) as well as mental retardation

Cretinism

# Growth Hormone Deficiency - The most common etiology in adult cases of growth factor deficiency - An onset type of GH deficiency - A tumor blocks the release of GH

Pituitary Adenoma

# Growth Hormone Excess - A pituitary tumor is the cause for the hypersecretion of GH - Happens pre-puberty before the closure of epiphyseal plates of long bones

Gigantism

# Growth Hormone Excess - Occurs after puberty - There is enlargement of the hands and feet, coarse facial features, visceromegaly (cardiomegaly), skin thickening, osteoarthritis, and hyperglycemia

Acromegaly

# Laboratory Diagnosis of GH Disorders What analytical method is commonly used?

Chemiluminescent assays

# Laboratory Diagnosis of GH Disorders - Blood is collected from the patient after a complete ____-minute rest - (Fasting/Non-fasting) specimen is required

1. 30 2. Fasting (atleast 8 hours)

# Laboratory Diagnosis of GH Deficiencies 1. What is the screening test? 2. What are the 2 confirmatory tests?

1. Physical Activity Test 2. Insulin Tolerance and Arginine Stimulation Test

# Confirmatory Tests for GH Deficiencies - The former gold standard for the detection of GH deficiencies - There is induced hypoglycemia by a chemical (IIH) - Undergoes a 24-hour or nighttime monitoring - Normal values for adults are > 5 ng/mL while for children it's > 10 ng/mL

Insulin Tolerance Test | Note: Hypoglycemia is the most potent stimulus for GH

# Confirmatory Tests for GH Deficiencies - Also undergoes 24-hour or nighttime monitoring - Has a normal reference value of > 4.1 ng/mL

Arginine Stimulation Test

# Confirmatory Tests for GH Excess (Suppression Tests) This screening test is ↑ in Acromegaly but ↓ in GH deficiency

Somatomedin C/ IGF-1 Test

# Confirmatory Tests for GH Excess (Suppression Tests) - Makes use of 75g of the OGTT load - A baseline glucose level (FBS) is collected and then after that it's the GH measurement every 30 minutes for 2 hours (total of 5 samples total) - The normal result is < 1 ng/mL while > 1 ng/mL is indicative for acromegaly

Glucose Suppression Test

# Hormones of the Anterior Pitutary Refers to FSH and LH which are markers for diagnosing fertility and menstrual cycle disorders

Gonadotropins

# Gonadotropins FSH or LH? 1. In males - helps Leydig cells produce testosterone 2. In males - aids in spermatogenesis 3. In females - for ovulation and final follicular growth and androgen (estrogen and progesterone) synthesis by thecal cells

1. LH 2. FSH 3. LH

# Gonadotropins Increased LH, FSH, or both? 1. Lack of estrogen after menopause 2. During premature menopause

1. Increased for both 2. Increased FSH

# Hormones of the Anterior Pitutary - Important for the stimulation of the follicular thyroid cells to produce T3 and T4 (aka thyrotropin) - The main stimulus for the uptake of iodide by the thyroid gland - Composed of mono-covalently linked alpha and beta subunits

Thyroid Stimulating Hormone (TSH)

# Thyroid Stimulating Hormone (TSH) Alpha or Beta Subunit? 1. For hormonal activities 2. TSH, LH, FSH, and HCG

1. Beta 2. Alpha

# Hormones of the Anterior Pitutary - A single chain peptide without disulfide bonds - Produced in response to low serum cortisol (positive feedback) - A regulator of adrenal androgen synthesis - The highest levels are found between 6am to 8am while the lowest are found between 6pm to 11pm (diurnal variation)

Adrenocorticotrophic Hormone (ACTH)

# Cushing's Disease vs. Syndrome 1. Characterized by increased ACTH and cortisol 2. Characterized by decreased or normal ACTH but with increased cortisol (there is a problem with the adrenal glands)

1. Cushing's Disease 2. Cushing's Syndrome

# Hormones of the Anterior Pitutary - Increased in cases of Addison's disease, ectopic tumors, after protein-rich meals, and Cushing's disease - Deficiency of this presents with atrophy of the zona glomerulosa and reticularis of the adrenal cortex

Adrenocorticotrophic Hormone (ACTH)

# Hormones of the Anterior Pitutary - A pituitary lactogenic hormone (stimulates the mammary glands to produce milk), stress hormone, and direct effector hormone - Is majorly inhibited by dopamine and results to hypogonadism when in excess

Prolactin

# Hormones of the Anterior Pitutary This in increased in cases of: pituitary adenoma, infertility, amenorrhea, galactorrhea, acromegaly, renal failure, PCOS, cirrhosis, and primary and secondary hypothyroidism

Prolactin

# Hormones of the Anterior Pitutary Its physiologic stimuli include exercise, sleep, stress, pain, and nipple stimulation during breastfeeding

Prolactin

# Hormones of the Anterior Pitutary Its pharmacologic stimuli include Verapamil, Phenothiazines, Olanzapine, Prozac, Cimetidine, and Opiates

Prolactin

# Endocrine Glands - Aka neurohypophysis - Can only release hormones that are produced in the hypothalamus (oxytocin and vasopressin/ADH)

Posterior Pituitary Gland

# Hormones of the Posterior Pitutary - A nonapeptide - Secreted in association with a carrier protein - Functions for milk ejection and the stimulation of uterine contractions at term (aka the Fergusson reflex)

Oxytocin

# Hormones of the Posterior Pitutary - Aka Arginine-Vasopressin or ADH - Also a nonapeptide - The target tissues are the DCT and collecting tubules of the kidneys for water reabsorption

Vasopressin

# Hormones of the Posterior Pitutary Its physiologic stimuli for secretion/production are: decreased BP (main stimulus), nausea, hypoglycemia, hypercarbia, and nicotine

Vasopressin

# Hormones of the Posterior Pitutary Its physiologic stimuli to release incudes: dehydration, physical stress, emotional stress, and surgery

Vasopressin

# Hormones of the Posterior Pitutary The ff. are inhibitors for the release of what hormone? - Ethanol, cortisol, lithium, and demeclocycline

Vasopressin

# Disorders of Vasopressin - Excess ADH leads to excess water in the body - Manifests with hyponatremia and hypo-osmolality (dilution effect due to excess water)

Syndrome of Inappropriate ADH Secretion (SIADH)

# Disorders of Vasopressin A condition correspondent to ADH deficiency leading to polyuria, polydipsia, and polyphaga (3Ps)

Diabetes Insipidus

# Disorders of Vasopressin (Types of DI) Neurogenic or Nephrogenic DI? 1. ADH is deficient but with normal receptors 2. ADH is normal but with defective receptors (resistance to ADH action)

1. Neurogenic 2. Nephrogenic

# Disorders of Vasopressin (Types of DI) Give the other names of neurogenic diabetes insipidus

True/Hypothalamic/Central Diabetes Insipidus

# Laboratory Diagnosis of Diabetes Insipidus - Aka overnight water deprivation test - Should be NPO for 8-12 hours - A level of < 300 mOsm/kg is indicative for DI since it should increase overnight if the ADH is normal - The normal level is 275-295 mOsm/kg

Concentration Test

# Laboratory Diagnosis of Diabetes Insipidus Neurogenic or Nephrogenic? 1. If ADH is decreased and you administer exogenous ADH = Rapid water reabsorption 2. If ADH is normal or increased and you administer exogenous ADH = No effect on reabsorption

1. Neurogenic 2. Nephrogenic