Endocrine System: Pituitary Hormones Quiz

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Questions and Answers

What is a primary cause of hypo- or hypersecretion of anterior pituitary hormones?

Deficiencies in nutrition and diet

Obesity and body composition changes

Effects of hypophysiotropic hormones

Hypo- or hypersecretion of anterior pituitary cells (correct)

Which factor does NOT influence the secretion pattern of Growth Hormone?

Age and gender

Chronic diseases

Air quality in the environment (correct)

Normal levels of other hormones

Which of the following statements regarding Growth Hormone is true?

It is a single chain composed of 200 amino acids

It solely determines the final height and growth in individuals

Its secretion remains constant throughout life

It contributes to body growth but is not the only factor (correct)

What is the role of somatostatin in relation to growth hormone?

Inhibits the action of GHRH and the release of growth hormone Signup and view all the answers

What condition occurs due to defects in the levels of Prolactin?

Difficulties in lactation and reproductive health Signup and view all the answers

Which condition is associated with a deficiency of growth hormone in children?

Laron Dwarfism Signup and view all the answers

What is the primary role of ADH/Vasopressin in the body?

Controlling kidney function and water retention Signup and view all the answers

What symptoms might an adult with growth hormone deficiency experience?

Decreased bone density and increased risk of heart failure Signup and view all the answers

What initial test is recommended to measure growth hormone deficiency?

IGF-1 levels Signup and view all the answers

What can cause a defect in GH production?

Underactivity of somatotrophs Signup and view all the answers

What is the primary cause of nephrogenic diabetes insipidus?

Renal disease or mutations in ADH receptor gene Signup and view all the answers

Which of the following symptoms is NOT commonly associated with diabetes insipidus?

Hyponatraemia Signup and view all the answers

What is the first-line treatment for syndrome of inappropriate ADH secretion (SIADH)?

Fluid restriction Signup and view all the answers

What major effect is caused by excess levels of ADH in the bloodstream?

Hyponatraemia due to water retention Signup and view all the answers

Which one of the following is a notable symptom of severe hyponatraemia?

Confusion and seizures Signup and view all the answers

What is the primary function of Arginine Vasopressin (ADH)?

Enhances water retention by kidneys Signup and view all the answers

Which receptors are stimulated by high concentrations of ADH, resulting in increased blood pressure?

V1 receptors in skin and mesenteric blood vessels Signup and view all the answers

Which factors are known to inhibit ADH secretion?

Plasma hypoosmolality Signup and view all the answers

What condition is characterized by a deficiency in ADH secretion?

Diabetes insipidus Signup and view all the answers

What is the effect of increased serum osmolality on ADH secretion?

Stimulates ADH secretion Signup and view all the answers

What is the primary function of Growth Hormone (GH)?

Promotes bone and muscle growth Signup and view all the answers

What happens to the average plasma concentration of growth hormone as a person ages?

It decreases gradually Signup and view all the answers

Which hormone is known to restrain the release of ADH?

Cortisol Signup and view all the answers

What condition can result from a deficiency of Prolactin?

Lack of lactation Signup and view all the answers

Which hormone is primarily responsible for mediating the growth-promoting effects of growth hormone?

Somatomedin C Signup and view all the answers

What disorder is caused by an excess of Antidiuretic Hormone (ADH)?

SIADH Signup and view all the answers

What is the relation between severe volume loss and ADH secretion?

It causes a hypertonic state, triggering ADH release Signup and view all the answers

How sensitive are volume receptors compared to osmoreceptors in regulating ADH secretion?

Less sensitive, requiring a larger change in volume Signup and view all the answers

What is the major source of circulating IGF-1 in the body?

Liver Signup and view all the answers

Which hormone plays a crucial role in social bonding and labor?

Oxytocin Signup and view all the answers

What is a potential effect of excess Growth Hormone (GH) in adults?

Acromegaly Signup and view all the answers

At what age range is the average plasma concentration of growth hormone the highest?

5-20 years Signup and view all the answers

Which statement about the secretion of growth hormone is correct?

It can have significant effects even after the growth period Signup and view all the answers

Which disorder is linked to a deficiency in ADH?

Diabetes insipidus Signup and view all the answers

What is the primary consequence of excess Prolactin in women?

Infertility Signup and view all the answers

Growth hormone primarily exerts its effects by acting directly on target cells. True or False?

False Signup and view all the answers

What is the concentration of growth hormone in an otherwise normal person aged 40-70 years?

1.6 ng/ml Signup and view all the answers

Which hormone is primarily responsible for regulating water balance in the body?

ADH/Vasopressin Signup and view all the answers

Which of the following hormones is structurally similar to somatomedins?

Insulin Signup and view all the answers

What is a key symptom of growth hormone excess in childhood?

Rapid growth in height Signup and view all the answers

Which treatment is commonly used for growth hormone deficiency?

Recombinant forms of human growth hormone Signup and view all the answers

How does acromegaly typically manifest after adolescence?

Soft tissue thickening Signup and view all the answers

What complication is commonly associated with growth hormone excess?

Cardiac hypertrophy Signup and view all the answers

What is a potential consequence of untreated growth hormone excess in childhood?

Higher susceptibility to infections Signup and view all the answers

Which of the following conditions can lead to nephrogenic diabetes insipidus?

Mutations in ADH receptor gene Signup and view all the answers

What is a major effect of the syndrome of inappropriate ADH secretion (SIADH)?

Hyponatraemia and hypo-osmolar plasma Signup and view all the answers

Which of the following symptoms is associated with severe hyponatraemia from SIADH?

Confusion and seizures Signup and view all the answers

What is the first-line treatment for managing SIADH?

Fluid restriction Signup and view all the answers

What is true regarding the effects of exogenous ADH treatment in central diabetes insipidus?

It aids in water conservation by the kidneys. Signup and view all the answers

What primarily stimulates the secretion of ADH due to hyperosmolar conditions?

Rising serum osmolality Signup and view all the answers

Which statement correctly describes the effect of ADH on the kidneys?

Promotes water retention Signup and view all the answers

How does hypovolemic shock affect ADH secretion?

It triggers an increase in ADH release. Signup and view all the answers

Which condition is primarily associated with excessive release of ADH?

Syndrome of inappropriate ADH secretion (SIADH) Signup and view all the answers

What is the relative sensitivity of volume receptors compared to osmoreceptors in regulating ADH secretion?

Less sensitive than osmoreceptors Signup and view all the answers

What physiological changes occur at very high concentrations of ADH?

Vasoconstriction and raised blood pressure Signup and view all the answers

How do cortisol and thyroid hormones influence ADH secretion?

They inhibit ADH release. Signup and view all the answers

What triggers the release of ADH in situations of plasma hypovolemia?

Plasma volume depletion Signup and view all the answers

Which hormone primarily mediates the growth-promoting effects that are associated with growth hormone?

Insulin-like growth factor 1 (IGF-1) Signup and view all the answers

What is primarily responsible for the release of circulating IGF-1 into the blood?

The liver on stimulation by GH Signup and view all the answers

In which age range is the average plasma concentration of growth hormone the lowest?

40-70 years Signup and view all the answers

What do somatomedins primarily exert in relation to growth hormone?

Growth-promoting effects indirectly Signup and view all the answers

What is one potential consequence of continuous secretion of growth hormone beyond the normal growing period?

Metabolic effects on various tissues Signup and view all the answers

How does growth hormone primarily interact with its target tissues to exert effects?

By stimulating the production of somatomedins Signup and view all the answers

At what age does the average plasma concentration of growth hormone begin to notably decline?

After 20 years Signup and view all the answers

Which action of growth hormone directly promotes the growth of long bones?

Acts on long bone epiphyseal plates via IGF-1 Signup and view all the answers

How does growth hormone affect glucose levels in the body?

Conserves glucose for the brain Signup and view all the answers

What is a metabolic effect of excess growth hormone secretion?

Increased likelihood of developing type II diabetes Signup and view all the answers

What is the primary function of insulin-like growth factor 1 (IGF-1) in relation to growth hormone?

Mediates the growth-promoting effects of growth hormone Signup and view all the answers

Which physiological condition triggers the secretion of growth hormone?

Hypoglycemia and fasting Signup and view all the answers

In which way does growth hormone influence body composition in adults?

Increases lean body mass through protein synthesis Signup and view all the answers

Which of the following is NOT a direct effect of growth hormone on tissues?

Promotes protein degradation in muscles Signup and view all the answers

What role does somatostatin play in the regulation of growth hormone secretion?

Inhibits growth hormone release Signup and view all the answers

What is the primary reason for the significant increase in height observed in the 10-year-old boy presenting with rapid growth?

Persistent high levels of Growth Hormone causing prolonged growth Signup and view all the answers

Which hormone's elevation is primarily associated with spontaneous lactation in the 35-year-old woman with a pituitary adenoma?

Prolactin Signup and view all the answers

What mechanism explains the low urine osmolality despite elevated serum sodium in the 50-year-old man?

Inability to concentrate urine due to lack of ADH action Signup and view all the answers

In the case of the pregnant woman experiencing contractions, what role does the hormone oxytocin primarily play?

Facilitating uterine contractions and promoting labor progression Signup and view all the answers

What is the expected outcome following treatment with desmopressin in the patient diagnosed with central diabetes insipidus?

Decreased thirst and increased urine osmolality Signup and view all the answers

Which of the following clinical signs would indicate a worsening condition in the 10-year-old boy diagnosed with gigantism?

Significant loss of visual acuity Signup and view all the answers

Which of the following statements regarding the initial approach to treating the woman's pituitary adenoma is accurate?

Dopamine agonist therapy can effectively reduce prolactin levels before considering surgery. Signup and view all the answers

What are the key features that help distinguish gigantism from acromegaly?

Gigantism occurs before epiphyseal closure in children, whereas acromegaly occurs after. Signup and view all the answers

Study Notes

Hypothalamus-Pituitary Target Organ Axes: Feedback Control

Learning Outcomes: Covering the role of Growth Hormone, Prolactin, Oxytocin, and ADH/Vasopressin, and how defects in their levels cause disease
Class: Year 2 Endocrine and Breast Module
Lecturer: Dr. Brona Murphy and Dr. Ebrahim Rajab
Date: January 2024

Anterior Pituitary Hormones

General: Specific hypo- and hyper-secretory conditions exist for most anterior pituitary hormones
Causes: Conditions are caused by either
- Primary: Hypo or hypersecretion of the anterior pituitary cells
- Secondary: Hypo or hypersecretion of hypophysiotropic hormones

Growth Hormone (Somatotropin)

Structure: Single chain, 191 amino acids
Role in Growth: Essential for growth, but not solely determining final growth rate. Genetic factors, adequate diet, and absence of chronic disease/stress are also important
Secretion: Pulsatile, serum concentration varies with age, gender, nutrition, sleep, body composition, stress, and exercise
Measurement: Random serum GH measurement can be misleading, so diagnostic testing may require additional methods

Growth Hormone in the Body

Concentration & Age: Average plasma GH concentrations decline with age. Levels are 6 ng/ml (5-20 years), 3 ng/ml (20-40 years), and 1.6 ng/ml (40-70 years)
Metabolic Actions (Adults): Acts on liver, muscle, and adipose tissue to shift metabolism to lipid use for energy, conserving carbohydrates and proteins. It raises blood glucose (antagonizes insulin) and increases lipolysis.
Overall Functions: Maintains adult cardiac function (contractility) and glucose homeostasis and supports bone mineralization, adipose balance, and muscle anabolism
Biological Actions: Influences numerous tissues, promoting protein synthesis, influencing cell growth and function, and affecting lipid and carbohydrate metabolism.

Growth Hormone Promoting Effects

Somatomedins (IGFs): GH acts indirectly on target cells via somatomedins, primarily IGF-1, which is majorly produced by the liver
Growth Promotion: Stimulates linear growth via hyperplasia (increased cell division) and hypertrophy (increased protein synthesis) of bone and other organs
Bone Growth: GH directly and indirectly promotes bone growth in thickness and length via IGF-1. It also stimulates chondrocytic and osteogenic cells

Role of Growth Hormone in the Body - Metabolic Actions

Lipolysis and Lipid Oxidation: Increases fatty acids in the blood
Protein Synthesis: Stimulates protein synthesis in most cells, particularly muscles
Glucose Homeostasis: Raises blood glucose, counteracting the effects of insulin. Decreases peripheral insulin sensitivity, reducing glucose uptake by muscles
Diabetogenic Effect: Because GH leads to insulin insensitivity/resistance, it can produce metabolic disturbances similar to type II diabetes
Electrolyte Balance: Promotes phosphate, water, and sodium retention

Role in Overall Functions

Adult Cardiac Function and Glucose: Maintains adult cardiac function (contractility) and glucose homeostasis
Other Functions: Supports bone mineralization, adipose balance, and muscle anabolism

Role of Growth Hormone in the Body - Other Aspects

Causes of GH Deficiency:
- Hypothalamic dysfunction, defect in GHRH
- Pituitary defect, defect in GH production
- Receptor defect, target cells failing to respond to GH
Symptoms of GH Deficiency: vary depending on age (dwarfism in children, reduced skeletal mass/increased body fat in adults)
Measuring GH Deficiency: testing IGF-1, followed by provocative testing (insulin-induced hypoglycemia)
Treatment of GH Deficiency. Recombinant human GH

Causes of Growth Hormone Excess

Tumors of GH Producing Cells: Anterior pituitary tumour

Symptoms of Growth Hormone Excess

Gigantism (Childhood): Rapid growth in height without proportional distortion of body
Acromegaly (Adulthood): Enlargement of hands, feet, jaw, and thickening of skin, bones. Increased cardiovascular mortality.

Prolactin

Secretion: Secreted by lactotropes in the anterior pituitary
Structure: 199-amino acid single chain protein
Primary Role: Stimulates milk production
Differences from other endocrine cells:
Not part of an endocrine axis
Predominantly under tonic inhibitory control by dopamine from hypothalamus
Dysfunction: Disruption of the pituitary stalk can lead to increased PRL, while other anterior pituitary hormones can decrease
Regulation: Tonically inhibited by dopamine, stimulated by prolactin-releasing factors (PRFs) under certain conditions such as suckling, stress, and estrogen
Effects in Women: Stimulated by elevated estrogen during pregnancy. Inhibits GnRH (and thus prevents ovulation) and stimulates breast development and milk production. Suckling maintains elevated PRL
Effects in Men: Not part of the normal male reproductive hormone feedback loop. It inhibits GnRH, potentially impacting spermatogenesis
Causes of Excess Prolactin: Physiological (pregnancy, breastfeeding, stress) and pathological (pituitary adenoma, drug-induced)

Prolactin Deficiencies

Causes: Isolated PRL deficiency is rare. Often associated with other pituitary hormone deficiencies
Symptoms: Decreased lactation

Lactotroph Adenoma

Commonest pituitary tumour: often the cause of female infertility
Treatment: First line medication with dopamine agonists (Cabergoline/Bromocriptine). Second line is surgery (transsphenoidal resection), radiation reserved for resistant/aggressive tumours

Oxytocin

Role in Pregnancy & Labor: Increases gradually, sharply during labour. Stimulates uterine contractions; promotes milk ejection following delivery
Social Interactions: Important for social interactions, including sexual arousal, recognition, trust and mother-infant bonding

Antidiuretic Hormone (ADH)/Vasopressin

Structure & Formation: Arginine vasopressin (AVP); Primarily formed in the supraoptic nuclei of hypothalamus
Regulation of Osmolarity: Regulates urinary water loss, ECF, and osmolarity.
Two Main Effects:
- Antidiuretic Effect: Enhances water retention by kidneys by increasing permeability of distal/collecting tubules to water; decreased urinary output.
- Pressor Effect: Causes contraction of arterioles
Release Regulation: Controlled by hypothalamic osmoreceptors and systemic baroreceptors.
Osmoreceptors: Maintain ECF within 280-295 mOsm/kg, a 1% rise in serum osmolality triggers ADH secretion.
Volume Receptors: Less sensitive than osmoreceptors; a 10-15% volume change leads to ADH changes
Inhibition: Cortisol and thyroid hormone restrain ADH release.

ADH Deficiency

Causes: Diabetes insipidus from posterior pituitary (hypothalamic central DI)
Causes Related to the Kidneys: Renal disease, mutations, and drugs (lithium)
Symptoms: Polyuria (excessive urination) and polydipsia

ADH Over-Secretion (SIADH)

Causes: Central nervous system (CNS) damage or secretion from abnormal sites (e.g., lung cancer)
Effects: Electrolyte disturbance (hyponatremia), initial mild CNS symptoms, low urinary output.

Summary:

Covering various hormones, their regulation, and disruptions affecting numerous body functions including homeostasis, reproduction, and growth.
Each section describes the hormone, its function, and disorders related to either over- or underproduction.

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Description

Test your knowledge on the endocrine system, specifically focusing on anterior pituitary hormones. This quiz will cover topics such as growth hormone, ADH, prolactin, and their associated conditions. Assess your understanding of hormone secretion patterns and their physiological impacts.