Hormones and reproductive systems Flashcards
What are endocrine glands?
Organs that secrete a hormone into the blood
What are hormones?
Chemical messengers
Regulate processes like growth, development, metabolism, homeostasis and reproductive processes
Name three types of hormones.
Steroid hormones
Peptide hormones
Amino acid derived hormones
What are some steroid hormones?
Testosterone
Oestrogen
Cortisol
What are some peptide hormones?
Growth hormone
Oxytocin
Parathyroid hormone
What are some amino acid derived hormones?
Thyroid hormones
Catelcholamines
What is the pituitary gland?
A small structure at the base of the brain which releases hormones that, in turn, controls the activity of the body’s other hormone glands
What are the 2 hormones released by the posterior pituitary?
Oxytocin
Vasopressin (Anti-diuretic hormone, ADH)
What does oxytocin do?
Controls milk release from lactating breast
Controls uterine contraction at onset of labour
What does vasopressin/ ADH do?
Acts on kidneys to reabsorb water
Regulates blood osmolarity and urine output
Describe the neuro-endocrine reflex that happens with breastfeeding?
Suckling -> Hypothalamus -> Posterior pituitary -> Oxytocin -> Milk squeezed out
What are the 6 hormones secreted by the anterior pituitary?
1) Growth hormone
2) Prolactin
3) Adrenocorticotropic hormone (ACTH)
4) Thyroid stimulating hormone (TSH)
5) Follicle stimulating hormone (FSH)
6) Luteinising hormone (LH)
What do most of the anterior pituitary’s hormones do?
Most of which regulate secretions of tropic hormones
What are tropic hormones?
Hormones from endocrine organs
What are the principle target organs for FSH and LH?
Ovaries and testes
What is the principle target organ for ACTH (Adenocorticotropic hormone)?
Adrenal glands
What is the principle target organ for TSH (Thyroid stimulating hormone)?
Thyroid gland
What are the principle target organs for growth hormone?
Bone
Skeletal muscle
Liver
What are the principle target organs for prolactin?
Mammary glands
How can you remember the anterior pituitary hormones?
FLAT PeG
What are the 5 cell types in the anterior pituitary?
Somatotrophs Lactotrophs Corticotrophs Gonadotrophs Thyrotrophs
What hormone is produced by the cell type, somatotrophs?
Growth hormone
What hormone is produced by the cell type, lactotrophs?
Prolactin
What hormone is produced by the cell type, corticotrophs?
Adrenocorticotropic hormone (ACTH)
What hormones are produced by the cell type, gonadotrophs?
Follicle stimulating hormone (FSH) Luteinising hormone (LH)
What hormone is produced by the cell type, thyrotrophs?
Thyroid stimulating hormone (TSH)
What triggers the release of anterior pituitary hormones?
Hormones from the hypothalamus control release of anterior pituitary hormones
Describe growth hormone.
Synthesised and stored in somatotrophs
Principle targets: bone and skeletal muscle
Stimulates growth in children and adolescents but continues to have important impacts through adult life
What are the direct metabolic impacts of GH on muscle, adipose tissue and liver?
Increased muscle mass
Decrease in fat deposits
Stimulates IGF (insulin-like growth factors) production
What causes growth hormone disorders?
Usually result of pituitary tumour secreting growth hormone
What is gigantism and what is it caused by?
GH excess
Abnormally high linear growth due to excessive action go IGF while epiphyseal growth plates are open (childhood)
Normal body proportions because soft tissue is also impacted
What is acromegaly and what is it caused by?
GH excess
Increased growth hormone later in life after fusion of epiphyses
Course facial features, enlarged hands and feet, protruding jaw, separation of teeth, enlarged tongue and thickened lips, deep voice, cardiomegaly and diabetes
Usually due to pituitary tumour
What is the result of GH insufficiency in adults generally?
No major symptoms
What is the result of GH insufficiency in children?
Pituitary dwarfism Slow growth rate Normal body proportions Poor muscle development Excess subcutaneous fat
Describe the thyroid gland.
Discrete organ, adheres to trachea
2 large, asymmetrical flat lobes connected by isthmus
Rich blood supply
Regulated by hypothalamus and pituitary
What is the functional unit of the thyroid gland? How many are there in each gland?
Follicle
1000s in each gland
Consists of a layer of follicular cells surrounding a colloid-filled cavity
What are the thyroid hormones?
Triiodothyronine (T3)
Thyroxine (T4)
Describe the thyroid hormones.
Amino acid derived hormones
Tyrosine
Iodinated
What 2 principle raw materials are required for thyroid hormone synthesis?
Tyrosines: provided by thyroglobulin and secreted by follicular cells into lumen of follicle
Iodine: essential requirement, pumped into follicular cells against concentration gradient
What is one major advantage of the thyroid hormone system?
Capable of storing many weeks worth of thyroid hormone, coupled to thyroglobulin
If no iodine is available, thyroid hormone secretion will be maintained for a while
Where are thyroid receptors in the body?
Throughout the body e.g. liver, brain, kidney, hypothalamus and pituitary
Does T3 or T4 have a greater biological activity?
T3
Where does enzymatic conversion of T4 into T3 occur?
In peripheral tissues (liver and kidneys)
What are the principle actions of thyroid hormones?
Metabolism
Heat production (calorigenic effect)
Growth and development
Cardiovascular function
How do thyroid hormones impact metabolism?
Increases mobilisation and utilisation of glucose, fat and protein
How do thyroid hormones impact heat production?
Important in temperature regulation and adaptation to cold environments
How do thyroid hormones impact growth and development?
Essential for normal growth of tissues, including CNS
Synergy with growth hormone
Deficiencies in thyroid hormone can result in mental impairment and short stature
How do thyroid hormones impact cardiovascular function?
Increased cardiac output, heart rate and contractility
Increases ventilation rate
How does TSH impact thyroid function?
Stimulates every aspect of thyroid function including:
Promoting release of thyroid hormones
Increasing activity of iodide pump and iodination of tyrosine -> increases production of thyroid hormones
What is hypothyroidism and what does it cause?
Underactive thyroid
In general, metabolic rate decreases and weight gain
Dry, cold skin, sensitive to cold, impaired memory, mental dullness, lethargy
What is hyperthyroidism and what does it cause?
Overactive thyroid
In general, metabolic rate increases and weight loss
Loss of weight, excessive sweating, intolerance to heat, anxiety, nervousness and exophthalamus
How do you diagnose and treat hypothyroidism?
Reduced metabolic rate Slow pulse Reduced cardiac output Low plasma levels of 'free' T3 and T4 Thyroxine, dose determine by TSH monitoring
What are some causes of hypothyroidism?
Iodine deficiency (endemic goitre) Autoimmune disease: Hashimoto's thyroiditis
What is iodine deficiency (endemic goitre)?
Insufficent dietary iodine
Insufficient amounts of T3 and T4
Abnormally high TSH
Abnormal growth of thyroid due to trophic effects of TSH
What is Hashimoto’s disease?
Most common cause of hypothyroidism Autoimmune disease Antibodies against TSH receptor Prevents TSH binding its receptor Prevents stimulation of hormones Also antibodies against thyroid peroxidase and thyroglobulin Leads to thyroid gland destruction
What is congenital hypothyroidism?
Lack of gland or incorrect hormone biosynthesis
Mental retardation if treatment later than 3 months
What is the clinical exam of hyperthyroidism?
Raised metabolic rate
Oxygen consumption
Increased heart rate
Hypertension
How do you treat hyperthyroidism?
Surgical removal of all or part of thyroid
Ingestion of radioactive iodine to selectively destroy most active thyroid cells
Drugs interfere with gland
What autoimmune disease causes hyperthyroidism? What are the characteristics of the disease?
Grave’s disease
Abnormal antibodies that mimic TSH
Activates TSH receptor inducing T3/T4 release
Characterised by goitre, exophthalmos and lid retraction, muscle weakness, heart palpitations and irritability
What is exophthalmus?
Bulging of the eye anteriorly around the orbit
Describe the position and structure of the adrenal glands.
A pair: lie flat on kidneys
Each gland enclosed by fibrous capsule surrounded by fat
Each gland equivalent to 2 endocrine glands
Inner: adrenal medulla
Outer: adrenal cortex
How does blood flow through the adrenal glands?
Rich blood supply: adrenal arteries arise
Blood flows through cortex and drains into medulla
Describe the adrenal medulla. Why is it not a true endocrine gland?
Modified part of sympathetic nervous system
Not a true endocrine gland as not under hormonal control
What are the 2 catecholamine hormones secreted by the adrenal medulla?
Adrenaline (epinephrine)
Noradrenaline (norepinephrine)
What is the medulla mainly composed of?
Chromaffin cells
What are the catelcholamine hormones used for?
Occurs as part of general sympathetic stimulation
Fight or flight response
Prepares body for acute stress
What are the major cardiovascular effects of adrenaline?
Increases heart rate and stroke volume
Increase in blood pressure
Vasodilation of coronary and skeletal muscle blood vessels
Vasocontriction of blood vessels in non-essential tissues
Bronchodilation
What are the major metabolic effects of adrenaline?
Increases amount of energy for immediate use
Liver converts glycogen to glucose
Metabolic rate increases
Blood flow changes, reducing digestive system activity and urine output
What are the 3 morphological distinct zones in the adrenal cortex?
Zona Glomerulosa
Zona Fasciculata
Zona Reticularis
What does the Zona Glomerulosa in the adrenal cortex produce?
Mineralocorticoids like aldosterone
What does the Zona Fasciculata in the adrenal cortex produce?
Glucocorticoids like cortisol
What does the Zona Reticularis in the adrenal cortex produce?
Gonadocorticoids like androgens
What do androgens do in males and females?
Males: role not fully understood, most sex steroids made in gonads
Females: Growth of pubic and auxiliary hair, sex drive, important source of androgens
What does aldosterone do?
Control extra-cellular fluid volume
Conserve body sodium
Stimulates reabsorption of sodium in renal distal convoluted tubules in exchange for potassium
What regulates aldosterone secretion?
Plasma levels of sodium and potassium via the renin-angiotensin-aldosterone system
What does cortisol do?
Mediates the body’s response to stress in response to endocrine signals
Stress= physical trauma, intense heat or cold, infection, mental or emotional trauma
What increases as a result of cortisol?
Increased catabolism (increases skeletal muscle protein catabolism) Increased lipolysis (liberate free fatty acids and triglycerides from adipose tissue= energy source) Increased intake (stimulates appetite)
What are some other general affects of cortisol?
Anti-inflammatory
Immunosuppressive
What controls cortisol release?
CRH: corticotrophin releasing hormone
ACTH: adrenocorticotrophic hormone. Maintains structural integrity of adrenal cortex and regulates secretion of glucocorticoid steroid hormones in response to stress
Describe Cushing’s Syndrome.
Overproduction of cortisol, as a result of adrenal tumour or pituitary tumour
Redistribute body fat, muscle wastage, thin skin, bruising abnormal pigmentation, changes in protein metabolism, hyperglycaemia, hypertension
What is Addison’s disease?
Rare
Damage to adrenal glands, autoimmune disease or pituitary damage
Deficits in glucocorticoids and mineralocorticoids
Progressive weakness, lassitude and weight loss
Pigmentation of skin and mucosal membranes
What are the many roles of calcium?
Structural component of bones and teeth
Maintains normal excitability of nerve and muscle cells
Impacts neurotransmitter and hormone release
Muscle contraction
Activation of enzymes
Coagulation of blood
Milk production
What is plasma calcium concentration?
2.2-2.6 mM
Why is plasma calcium so tightly regulated?
Too low= neuronal hyperexcitability
Too high= depression and kidney damage/ stones
How is plasma calcium regulated?
Hormonal control: balance maintained between ECF and 3 body compartment s
Control points were absorption via intestines, excretion via kidney/ urine and temporary storage via bones
What form must calcium be in before it can be absorbed?
Soluble and ionised
What are the 3 types of bone cells and what do they do?
Osteoblasts: synthesise an secrete collagen and promote deposition of calcium phosphate crystals, secretes factors that activate osteoclasts
Osteoclasts: promote resorption of bone
Osteocytes: essential role in exchange of calcium between ECF and bone
What is plasma calcium concentration determined by?
Net absorption of calcium from gastrointestinal tract
Net excretion of calcium in urine
Exchange of calcium with bone
What 3 hormones control plasma concentration?
Parathyroid hormone
1, 25-dihyrdoxycholecalciferol (calcitriol)
Calcitonin
Describe parathyroid hormone.
Peptide hormone Stored within chief cells Half life= 5 mins Secreted at low rate at all times Released in response to low blood calcium Exerts effect on bone, gut and kidneys
What does parathyroid hormone do?
Main target tissue: kidney and bone
Increase reabsorption of calcium from urine
Decrease urinary calcium in minutes
Increase expression of enzyme 1alpha-hydroxylase (activates vitamin D)
Increase osteoclast activity
Increase bone resorption
What is vitamin D converted to and where does it come from?
Converted to 1,25 dihydroxycholecalciferol (calcitriol)
Obtained from diet and synthesised in skin in presence of sunlight
What does calcitriol do?
Acts on cells in GIT to increase production of calcium transport proteins
Increases calcium uptake from GIT
Can increase calcium stores
Bone: increase rate of bone resorption
Kidney: minor effect in decreasing urinary loss of calcium
What does calcitonin do?
Secreted by parafollicular cells of thyroid gland
Lowers level of free plasma calcium
Inhibits osteoclast activity: bone resorption reduced
Increase excretion of calcium and phosphate by kidneys
What is hyperparathyroidism (hypercalcaemia)?
Inappropriate secretion of PTH, resulting in hypercalcaemia
Elevated PTH and raised serum calcium
Caused by parathyroid adenoma
Bones, stones, abdominal groans and psychic moans
What is caused by vitamin D deficiency (hypocalcaemia)?
Bone remodelling impaired
Failure of calcification
Children= skeletal deformities
Adults= softening of bone
What causes vitamin D deficiencies?
Poor diet
Malabsorption
Decreased sunlight
Liver of kidney disease
What are the primary female reproductive organs and what do they do?
Ovaries Produce ova (oogenesis) Secrete female sex hormones
What is oestrogen needed for?
Ova maturation and release
Establishing female secondary sex characteristics
Transport of sperm from vagina to fertilisation site
Contribute to treat development in anticipation of lactation
What is progesterone needed for?
Preparing suitable environment for nourishing a developing embryo/ foetus
Contributes to breasts’ ability to produce milk
What are the 2 alternating phases of the menstrual phase?
Follicular phase: first half of 28 day cycle
Maturing follicles that are producing oestrogen
Luteal phase: second half of 28 day phase
Presence of corpus luteum that produces progesterone and oestrogen
What is the corpus luteum and when does it form?
Ruptured follicle form corpus luteum
Releases large amounts of progesterone and oestrogen
Describe the process of fertilisation in the body.
Sperm deposited in vagina, travels through cervical canal, uterus ad up to upper 3rd of oviduct
Site of fertilisation: oviduct (upper third)
Must occur within 24-36 hours of ovulation
Sperm usually survive up to 2 days but can survive up to 7 days in female reproductive tract
What hormones are involved in lactation?
Elevated placental oestrogen and progesterone promote development of ducts and alveoli in mammary glands
Prolactin: stimulate synthesis of enzymes for milk production
Oxytocin causes milk ejection
Prolactin stimulates milk synthesis to replace milk ejected
