case 13 - tiredness Flashcards
1
Q
what main conditions can cause tiredness?
A
blood-related = anaemia, underactive thyroid, coeliac disease, diabetes, glandular fever
head-related = depression, anxiety
sleep-related = chronic fatigue syndrome, sleep apnoea, restless legs syndrome
2
Q
what’s the difference between tiredness and fatigue?
A
tiredness = can be relieved by sleep and rest
fatigue = overwhelming tiredness that cannot be relieved by sleep and rest
3
Q
what type of anaemias are associated with tiredness?
A
most commonly, iron-deficiency anaemia (type of microcytic anaemia)
also, vitamin B12 or folate deficiency anaemia (type of macrocytic anaemia)
4
Q
who is at a high risk of developing iron-deficiency anaemia?
A
women with heavy periods (menorrhagia)
pregnant women
5
Q
what is the most common cause of anaemia in men and postmenopausal women?
A
problems with the stomach and intestines
e.g. ulcer OR taking NSAIDs
6
Q
why and how can NSAIDs cause anaemia?
A
decrease the activity of blood platelets = decreased clot formation
= increased risk of bleeding and ulcer formation
= can lead to anaemia
7
Q
what is an ulcer?
A
a localised breach/sore (gap, erosion) in the surface continuity of the skin or mucous membrane (stomach, small intestine, oesophagus)
8
Q
besides anaemia, which (opposite) blood condition can cause tiredness?
A
haemochromatosis
9
Q
what is haemochromatosis?
A
rare inherited condition that affect men and women between 30-60
build-up of iron in the body leading to iron-overload
(deposition in the liver, joint pancreas etc)
10
Q
who does haemochromatosis affect most?
A
men and women between 30-60
11
Q
what is sleep apnoea?
A
a condition where your throat narrows or closes during sleep and repeatedly interrupts your breathing
12
Q
what does sleep apnoea result in?
A
loud snoring
decrease in blood oxygen levels
13
Q
what is the main symptoms/impact of sleep apnoea?
A
waking up often during the night
feeling exhausted the next day (due to disrupted sleep)
14
Q
who is affected by sleep apnoea the most?
A
overweight middle-aged men
15
Q
what factors worsen sleep apnoea?
A
increased alcohol and smoking
16
Q
what is an underactive thyroid?
A
too little thyroid hormone (thyroxine) in your body
due to reduced production by the thyroid gland
17
Q
besides tiredness, what are the additional symptoms of an underactive thyroid?
A
weight gain
aching muscles
dry skin
18
Q
what is an underactive thyroid alternatively known as?
A
hypothyroidism
19
Q
how can an underactive thyroid be diagnosed?
A
blood test (to test TSH, T4 levels)
20
Q
who is most likely to be affect by hypothyroidism?
A
women as they get older
21
Q
who is most likely to be affected by hypothyroidism?
A
women as they get older
22
Q
what is coeliac disease?
A
autoimmune condition wherein the immune system overreacts to the gluten ingested in the diet
(i.e. small intestine is hypersensitive to gluten = leading to difficulty in digesting food)
23
Q
what is gluten?
A
a protein in wheat, barley and rye
(helps foods maintain their shape, acting as a glue that holds food together)
24
Q
which foods are gluten-rich?
A
can be found in foods like pasta, bread, cakes and cereals
25
besides tiredness, what are the symptoms of coeliac disease?
diarrhoea
anaemia
bloating
weight loss
26
how is coeliac disease diagnosed?
blood test (specific)
27
what is chronic fatigue syndrome?
severe and disabling fatigue that goes on for at least 4 months
28
what is chronic fatigue alternatively known as?
myalgic encephalomyelitis
29
how long does ME usually last for?
at least four months
30
besides tiredness, what are the other symptoms of ME?
muscle or joint pain as well
31
which diabetes is tiredness a symptom of?
type 1 and type 2 diabetes both
32
besides tiredness, what are the symptoms of diabetes (type 1)?
polydipsia
polyuria
nocturia
weight loss
33
what is glandular fever?
a common viral infection that causes fatigue, along with fever, sore throat and swollen glands
34
besides tiredness, what are the symptoms of glandular fever?
fever
sore throat
swollen glands
35
who is most affected by glandular fever?
teenagers and young adults
36
how long does glandular fever last?
symptoms usually clear up in 4-6 weeks but fatigue can linger for several more months
37
how and why can depression cause tiredness?
core symptoms = anergia, anhedonia, low mood
can also cause disruption to sleep + early waking up = more tiredness during the day
38
what is restless legs syndrome?
an overwhelming urge to move your legs, which can keep you awake at night
39
what are the symptoms of restless legs syndrome?
an overwhelming urge to move legs at night
unpleasant crawling sensation
deep ache in legs
legs may jerk spontaneously through the night
40
why can restless legs syndrome lead to tiredness?
the urge to move/jerk legs or the deep ache of the leg muscles at night is so overwhelming = can keep people awake at night
= leading to tiredness
41
how can anxiety lead to tiredness?
constant uncontrollable feelings of anxiety that are so strong they interfere with their daily life
42
what is GAD?
generalised anxiety disorder
long-term condition that causes you to feel uncontrollably anxious about a wide range of situations and issues, rather than one specific event
43
who is most commonly affected by GAD?
common condition that affects women slightly more than men
44
besides tiredness, what else do people with GAD experience?
feelings of anxiety and irritability
45
to the nearest 10%, what percentage of patients who present to a GP with fatigue have a diagnosis made?
approx 66%
46
to the nearest 10%, what percentage of patients who present to a GP have a condition that is detected on blood tests?
approx \<10%
= highlights the importance of a good, comprehensive history and a good physical examination
47
how many GP consultations are due to fatigue?
approx 7%
48
name four other possible differential diagnoses
jet lag disorder
pregnancy
(chronic) heart failure
insomnia
vitamin D deficiency
( + many other reasons = lack of sleep, insomnia, medication, stress etc)
49
what is important to consider when thinking of possible differential diagnoses?
need to think of frequency e.g. common to rare AND consequence e.g. less serious (e.g. nutritional deficiencies) to very serious (e.g. cancers)
50
how do you narrow down to fewer/a maximum of two differential diagnoses?
by asking more questions
(i.e. taking a more comprehensive history)
51
which of the following blood tests would be ordered to investigate hypothyroidism?
FBC
U&E
vitamin D
TFTs
HbA1c
CRP
coeliac screen
autoimmune screen
EBV serology
FBC (full blood count)
U&E (urea & electrolytes)
vitamin D
TFTs (thyroid function tests)
HbA1c
52
why would a FBC be done to investigate tiredness?
to test for classic signs of anaemia, haematological malignancy and WBC levels for signs of infection
53
why would a U&E be done to investigate tiredness?
look at electrolyte abnormalities and eGFR
54
why would a vitamin D test be done to investigate tiredness?
to test for signs of vitamin D deficiency
55
why would TFTs be done to investigate tiredness?
to test for possible hypothyroidism
56
why would HbA1c be done to investigate tiredness?
family history of diabetes and to test for abnormal glucose levels
57
why wouldn't an autoimmune screen be done to investigate tiredness?
can be an extensive test that requires loads of time and effort so much justificatio is needed before requesting one
58
what do the following blood test results indicate and why?
indicate primary hypothyroidism due to the reduced fT3 and fT4 levels and the elevated TSH levels
59
what are the symptoms of hypothyroidism?
60
explain the mechanism of action of primary hypothyroidism, using the HPA axis
decreased production of thyroid hormones by the thyroid gland causes a compensatory increase of TSH due to the negative feedback loop
61
what is primary hypothyroidism?
low levels of blood thyroid hormone due to destruction of the thyroid gland
(destruction can be due to autoimmunity, surgery, radiation, medication etc)
62
what is secondary hypothyroidism?
either, more commonly, when the pituitary produces insufficient TSH
or
less commonly, when the hypothalamus produces insufficient thyrotropin-releasing hormone (TRH) = sometimes referred to as tertiary hypothyroidism
63
what would be the expected TFT results for a patient with primary hypothyroidism?
low fT3 and fT4
elevated TSH
64
what would be the expected TFT results for a patient with secondary hypothyroidism?
low fT3 and fT4
low TSH
65
differentiate between primary and secondary hypothyroidism
primary = due to direct damage to the pituitary gland
secondary = due to pituitary or hypothalamic damage/disease
66
what is tertiary hypothyroidism?
when the hypothalamus produces insufficient thyrotropin-releasing hormone (TRH)
reducing TSH and therefore fT3 and fT4 production downstream
67
what is the most common type of autoimmune hypothyroidism?
Hashimoto's thyroiditis
68
how can you differentiate between secondary and tertiary hypothyroidism?
practically impossible to do so as TRH levels are immeasurable (as it is in the portal circulation, not the systemic circulation)
so cannot tell if TSH levels are low due to hypothalamic/pituitary disease
= both fall under the category of secondary hypothyroidism sometimes
69
name the immune cells
eosinophils
basophils
neutrophils
macrophages
dendritic cells
natural killer (NK) cells
B lymphocytes
T lymphocytes
70
name the antigen-presenting cells
macrophages
dendritic cells
B cells
71
explain the mechanism by which immune cells attack the thyroid cells in Hashimoto's disease
the enzyme TPO (thyroid peroxidase) or thyroglobulin are abnormally processed by APCs as foreign antigens
circulating APCs present these antigens on their MHC II molecules to circulating T cells
the TCRs on T helper cells bind to the MHC II molecules on the APC
simultaneously, T-cell co-stimulation occurs when B7 on APCs binds to CD28 on T helper cells
TCRs on T helper cells then present the antigen to the MHC II molecules of B cells
simultaneously, B-cell co-stimulation takes place when CD40L on T cells binds to CD40 on B cells
upon activation, B cells will produce anti-TPO/anti-thyroglobulin (anti-Tg) antibodies to attack the thyrocytes
(T helper cells can also activate cytotoxic T cells to attack thyrocytes)
72
what are the 'foreign' antigens recognised by APCs in Hashimoto's?
either TPO (thyroid peroxidase) or thyroglobulin
73
how do APCs process the foreign antigens recognised?
circulating APCs present these antigens on their surface MHC II molecules to the TCRs of circulating T cells
74
how do APCs interact with T helper cells when a foreign antigen is recognised?
the TPO/Tg is presented in the MHC II molecules of APC to the TCRs of T helper cells
75
what are MHC I molecules?
receptors on the surfaces of almost all somatic cells that present endogenous antigens to cytotoxic T cells
76
what are MHC II molecules?
receptors on the surfaces of all antigen-presenting cells (dendritic cells, B cells, macrophages) that present exogenous antigens to T helper cells
77
differentiate between MHC I and MHC II molecules
MHC I = present on almost all somatic cells, present endogenous antigens (antigens found within the cytosol of human cells such as viral proteins, proteins from intracellular bacteria, and tumor antigens) to cytotoxic T cells
MHC II = present only on APCs, present exogenous antigens (antigens that enter from outside the body, such as bacteria, fungi, protozoa, and free viruses) to T helper cells
78
what is a TCR and what does it interact with?
a T cell receptor is a protein complex found on the surface of T cells and is responsible for recognising and binding to foreign antigens
interacts with antigens presented on the MHC II molecules of APCs
79
what is T cell co-stimulation?
a secondary signal which T cells rely on to activate an immune response in the presence of an antigen-presenting cell
= specifically when B7 on APCs binds to CD28 on T helper cells
80
why is T cell co-stimulation important?
to allow the immune response to continue and proceed
= for the T helper cell to actually process the antigen on the APC and then present it on other TCRs to B cells
81
how does a T cell process the foreign antigen in Hashimoto's?
presents the TPO/Tg foreign antigen to the BCRs of B cells via the TCRs
82
how do T helper cells interact with B cells when a foreign antigen is recognised?
the TPO/Tg foreign antigen is presented on the TCRs molecules of T cells to the BCRs of the B cells
simultaneously, B-cell co-stimulation takes place when CD40L on T cells binds to CD40 on B cells
83
what is B cell co-stimulation?
a secondary signal which B cells rely on to activate an immune response
when CD40L on T cells binds to CD40 on B cells
84
why is B cell co-stimulation important?
to allow the immune response to continue and proceed
= for the B cells to process the foreign TPO/Tg antigen and produce the corresponding anti-TPO/anti-Tg antibodies
85
which receptors interact in T cell co-stimulation?
B7 on APCs with CD28 on T helper cells
86
which receptors interact in B cell co-stimulation?
CD40L on T helper cells with CD40 on B cells
87
how do B cells respond after activation and B cell co-stimulation in Hashimoto's?
upon activation, B cells will produce anti-TPO/anti-thyroglobulin (anti-Tg) antibodies to attack the thyrocytes
(T helper cells can also activate cytotoxic T cells to attack thyrocytes)
88
what are anti-TPO antibodies?
antibodies that are produced against and attack the thyroid peroxidase (TPO) enzyme, which normally facilitates the production of thyroxine
89
what are anti-thyroglobulin antibodies?
antibodies produced against thyroglobulin (store for the inactive forms of the thyroid hormone in the follicular cells)
90
how are thyrocytes attacked in Hashimoto's?
upon activation, T helper cells can further activate cytotoxic T cells that go on to attack the thyrocytes
91
what is a BCR and what does it interact with?
a B cell receptor is a protein complex found on the surface of B cells that recognise and bind to foreign antigens
interact with TCRs on the surface of T helper cells
92
differentiate between exogenous and endogenous antigens
exogenous = antigens that enter from outside the body, such as bacteria, fungi, protozoa, and free viruses (MHC II)
endogenous = antigens found within the cytosol of human cells such as viral proteins, proteins from intracellular bacteria, and tumor antigens (MHC I)
93
differentiate between B cell receptors, surface immunoglobulins, and antibodies
structurally, all these are the same
- BCRs are membrane-bound and found on the surface of B cells
- surface immunoglobulins is an alternative term for BCRs
- antibodies are the secreted form of BCRs
94
why don't immune cells attack host cells?
ADAPTIVE (B and T cells)
- during development, B cells in the bone marrow and T cells in the thymus are exposed to the entire protein repertoire of the body = to prevent them from recognising self as foreign AND any self-reactive lymphocytes are destroyed early on
- a subpopulation of suppressive T cells, T regulatory cells (Treg cells) are potent mediators of self-tolerance + essential for the suppression of triggered immune responses if the antigen is a host antigen
INNATE
- granulocytes, macrophages and dendritic cells only attack cells that display PAMPs (pathogen-associated molecular patterns)
- NK cells attack only cells that lack MHC I molecules
95
what is immune tolerance and where does it occur?
central tolerance (both B cells and T cells) = the process of eliminating any self-reactive B/T lymphocytes
- B cell central tolerance occurs in the bone marrow: negative selection only
- T cell central tolerance occurs in the thymus: positive and negative selection both
96
how does immune tolerance take place in terms of adaptive immunity?
during development, B cells in the bone marrow and T cells in the thymus are exposed to the entire protein repertoire of the body = to prevent them from recognising self antigens as foreign AND any self-reactive lymphocytes are destroyed early on
(central tolerance in the primary lymphoid organs)
97
how does immune tolerance take place in terms of innate immunity?
- granulocytes (neutrophils, basophils, eosinophils), macrophages and dendritic cells only attack cells that display PAMPs (pathogen-associated molecular patterns)
- NK cells attack only cells that do not display MHC I molecules (which all somatic cells display normally)
98
what are PAMPs?
peptidoglycans, lipopolysaccharides, lipoteichoic acid, mannans, flagella proteins (structures found on pathogens/pathogen-infected cells)
99
why do normal granulocytes not attack body cells?
only attack cells that display PAMPs (pathogen-associated molecular patterns)
100
why do normal macrophages not attack body cells?
only attack cells that display PAMPs (pathogen-associated molecular patterns)
101
why do normal dendritic cells not attack body cells?
only attack cells that display PAMPs (pathogen-associated molecular patterns)
102
why do normal natural killer cells not attack body cells?
natural killers cells attack only cells that do not display MHC I molecules (which all somatic cells display normally)
103
when do autoimmune diseases occur?
when the immune system attacks the body's own cells, considering them to be foreign
(can be due to molecular mimicry, environmental triggers, genetic predisposition, high stress levels)
104
what is molecular mimicry?
when a foreign cells display antigens that resemble host antigens and so host antigens are mistaken as being foreign and responded to inappropriately
105
what are T regulatory cells and why are they important?
a subpopulation of suppressive T cells, T regulatory cells (Treg cells) are potent mediators of self-tolerance + essential for the suppression of triggered immune responses if the antigen is a host antigen
106
what are the steps to addressing tiredness in a GP setting?
- step 1 = define type of tiredness (i.e. drowsiness, short of breath, weakness)
- step 2 = why did this patient present?
look for functional impairment e.g. unable to make dinner for family
- step 3 = screen for red flags
lymphadenopathy, weight loss, specific malignancy features, joint pains, focal neurology, infective symptoms
- step 4 = explore any psychological triggers
work, money, family, mood, drugs and alcohol
- step 5 = examine the patient
- step 6 = initial bloods
FBC, ESR, TFTs, glucose
- step 7 = management of persisting unexplained tiredness with normal initial bloods
107
what are the types of tiredness?
drowsiness, short of breath, weakness
108
which one is more worrying?
1) 'i feel okay when i wake up, but it gets worse as i do things'
2) 'i feel rubbish when i wake up, but it gets better as i do things'
first one is worrying = exertional tiredness is far more likely to be physical
second one is not as worrying
109
what is important to assess initially when a patient presents with tiredness?
look for functional impairment (e.g. unable to make dinner for family)
110
what are the red flag symptoms associated with tiredness?
lymphadenopathy
unintentional weight loss
specific malignancy features (lung, breast, colon, upper GI and gynae)
joint pains and muscle aches
focal neurology
infective symptoms (glandular fever, TB, lyme disease)
111
what are possible psychosocial triggers for tiredness?
workload, money, family, mood, drugs & alcohol
112
how is a patient usually examined for tiredness?
dependent on history but at minimum: pulse, blood pressure and BMI
113
which bloods are taken initially from a patient presenting with tiredness?
FBC, TFTs, ESR, glucose
notes
- FBC = not just for anaemia, but also for iron deficiency and haematological malignancy
- in non-anaemia, menstruating women, treating a low ferritin can improve tiredness
- lymphomas often have normal WBC count in early stages
114
answer the following question posed by a patient with hypothyroidism:
'why did i get an underactive thyroid?'
- autoimmune damage = immune system attacks the thyroid gland and damages it so it cannot produce any more thyroxine (e.g Hashimoto's thyroiditis = most common; cause unclear but genetic predisposition and pre-existing autoimmune conditions are risk factors)
- previous thyroid treatment
- lack of dietary iodine (iodine is needed to produce thyroxine)
- pituitary problem
- viral infection
- medication
115
answer the following question posed by a patient with hypothyroidism:
'will i get better?'
yes, with treatment usually it will get better
treatment = replacing the deficient thyroid hormone in the form of a tablet (e.g. levothyroxine)
116
answer the following question posed by a patient with hypothyroidism:
'do i need treatment?'
yes, because your thyroid isn't making thyroid hormone resulting in your symptoms
to treat these symptoms we need to replace your thyroid hormone
this is usually done using tablets
117
answer the following question posed by a patient with hypothyroidism:
'what is the best treatment for me?'
the best treatment is daily hormone replacement tablets called levothyroxine
levothyroxine replaces the thyroxine hormone, which you're currently not making enough of
!! initial regular blood tests will be done until the correct dose of levothyroxine is reached - this may take some time to get right so may start on a low dose of levothyroxine which is then increased gradually as required !!
118
answer the following question posed by a patient with hypothyroidism:
'will i need to have treatment for the rest of my life?'
yes, you should take one tablet of levothyroxine at the same time every day, usually, the morning is recommended
you need to take levothyroxine for the rest of your life as an underactive thyroid is a lifelong condition
119
answer the following question posed by a patient with hypothyroidism:
'what are the side effects of treatment? how can i cope with them?'
levothyroxine doesn't usually have any side effects as the tablets are simply replacing a missing hormone
side effects would usually occur if you're taking too much levothyroxine which can cause problems including sweating, chest pain, headaches, diarrhoea and vomiting
(if symptoms develop then you should consult your doctor)
120
answer the following question posed by a patient with hypothyroidism:
'should i change what i eat?'
- effectiveness of levothyroxine can be altered by other medications, supplements or foods
- tablets should be swallowed with water on an empty stomach, and you should avoid eating for 30 minutes afterwards
- ensure you're getting adequate iodine in your diet as this is part of what makes thyroid hormone
(eating a balanced diet makes taking supplemental iodine unnecessary so just ensure you have a balanced diet)
121
answer the following question posed by a patient with hypothyroidism:
'what are the chances that someone else in my family will get an underactive thyroid? does it run in families?'
underactive thyroid is often caused by an autoimmune disease that can run through families
122
answer the following question posed by a patient with hypothyroidism:
'how will my treatment be managed if i wish to get pregnant?'
even more important that the treatment is followed as there are risks of several problems occurring during pregnancy (e.g. pre-eclampsia, anaemia in mother, underactive thyroid in baby, birth defects)
levothyroxine is usually safe to take in pregnancy
balanced diet recommended and take a prenatal multivitamin and mineral supplement containing iodine to receive most nutrients necessary for thyroid health
123
what are some common causes of an underactive thyroid gland?
autoimmune damage = self destructive process, body's immune system attack thyroid cells like foreign cells (most common form is Hashimoto's thyroiditis)
may happen temporarily after giving birth
radioactive iodine treatment or surgery to correct hyperthyroidism
antithyroid drugs if given for overactive thyroid disorder
medicines like lithium and amiodarone
some cough medicines containing large amounts of iodine
some health foods taken in excess e.g. kelp
malfunction of the pituitary gland
radiation for head and neck cancers, not so common in UK
congenital hypothyroidism = present from birth
124
what is the spectrum of symptoms experienced due to an underactive thyroid gland?
some people don't notice symptoms or have very mild symptoms that gradually develop
while others feel tired and low, have dry skin and hair loss
125
what are the symptoms of an underactive thyroid gland?
feeling tired or depressed
thinking more slowly or less clearly than usual (memory problems, difficulty in concentration)
having dry, flaky skin
hair loss
weight gain with a reduced appetite
cold intolerance
constipation
irregular periods, fertility problems and low libido
hoarse, croaky voice
slowed heart beat
reduced blood pressure
126
what is hormone replacement therapy for an underactive thyroid called?
levothyroxine (tablet)
127
how is levothyroxine taken?
tablet once a day on an empty stomach, usually before breakfast
128
how is the optimal dose of levothyroxine determined?
needs to be adjusted carefully to prevent administering too much
begin w a low dose that is gradually increased as required with regular monitoring through blood tests
129
how long does levothyroxine take to improve symptoms?
may take several weeks/months before you notice any difference in your symptoms
will have regular thyroid function tests during this time to inform dose adjustment
130
what can too much levothyroxine cause?
may get atrial fibrillation (abnormal heartbeat) or thinning of bones
131
how are patients with mildly underactive thyroid glands managed?
might not need to take thyroxine straight away
= may have your thyroid level checked regularly
132
what is congenital hypothyroidism?
hypothyroidism being present from birth
in some babies, the thyroid gland is underdeveloped and so there is a lack of thyroid hormone
133
how can hyperthyroidism lead to hypothyroidism?
treatment for hyperthyroidism (radioactive iodine therapy, surgery, antithyroid drugs) can lead to hypothyroidism
= if administered in excess
134
how is hypothyroidism diagnosed?
physical examination and blood tests
- physical examination = look for enlarge thyroid gland, brittle nails, hair loss, dry skin etc
- TFTs = assess TSH levels and fT3 and fT4 levels; can also test for thyroid antibodies (to confirm if the cause is autoimmune)
135
what is mild thyroid failure?
when the level of hypothyroidism so small that there are no obvious symptoms and can only be detected by blood test
136
what is mild thyroid failure also known as?
subclinical hypothyroidism
137
how is mild thyroid failure/subclinical hypothyroidism detected and diagnosed?
can be discovered as a result of blood tests for another autoimmune disorder or because there is a history of thyroid disorders in the family
blood test = raised TSH with a normal fT4 (indicates subclinical hypothyroidism)
138
how should subclinical hypothyroidism be managed?
regular thyroid function test and consult doctor if noticing any symptoms
139
what is levothyroxine?
a synthetic version of the thyroxine produced by the thyroid gland
140
what are the side effects of levothyroxine?
very pure, has negligible side effects when taken in the correct dose
141
how is levothyroxine dose determined normally?
doses are dependent upon the person’s body weight and their blood test results
most patients require between 100 and 150mcg a day, but the dose can be lower than 75mcg or up to
300mcg a day, depending on your needs
142
how is levothyroxine dose determined in severe hypothyroidism?
if severe hypothyroidism or risk of heart problems, doctor will start cautiously + increase dose gradually.
143
when is it best to take levothyroxine?
best taken in the morning with water on an empty stomach, at least 30 mins before eating and drinking anything
144
which drugs can decrease levothyroxine absorption and how is this prevented?
calcium, iron, cholesterol-lowering drugs (cholestyramine, colestipol), and multivitamin tablets
= levothyroxine is best taken at least four hours apart from them
145
which substances can decrease levothyroxine absorption and how?
grapefruit, as it increases acidity in the stomach
146
what happens if you miss a dose of levothyroxine?
easy to miss a levothyroxine tablet, but because your body has a big reservoir of thyroxine, you will not notice a difference
= important to take the tablets consistently every day as this can affect your blood test results and your health
147
what are the desired blood results for patients with hypothyroidism?
a TSH reading in the lower part of the reference range
and a fT4 reading towards the upper part or even slightly above the reference range
148
what is combined LT3 and LT4 therapy?
combo therapy of levothyroxine and tri-iodothyronine (LT4 and LT3) may be considered as an experimental approach under the supervision of an accredited endocrinologist
= if symptoms persist despite levothyroxine administration
149
why is LT3 not commonly prescribed?
not always available on the NHS
no solid evidence to suggest it has a better clinical outcome
150
what is the difference between brands of levothyroxine?
differences in fillers and bulking agents between the various brands of tablets
= why some people prefer specific brands of levothyroxine over others when they are all structurally the same
151
how does levothyroxine dose change when planning a pregnancy?
when planning = let doc know + have TFTs before
when pregnant = increased levothyroxine daily dose by 25-50mcg + then have regular TFTs
152
what is the risk of complications in a pregnant woman with hypothyroidism?
even if thyroid levesl not ideal = risk of pregnancy complications only slightly higher
= still good chance at successful pregnancy outcome
153
who looks after patients with hypothyroidism?
GP and endocrinologist
154
what happens in Hashimoto's thyroiditis?
variant of hypothyroidism, caused by autoimmunity
thyroid gets infiltrated by white cells (lymphocytic infiltration) and slowly loses its function = usually enlarges but may not
= may start with an over-active phase before becoming under-active (more common than reverse)
155
what are the two forms of autoimmune thyroidits?
Graves' disease and Hashimoto's thyroiditis
156
differentiate between Graves' disease and Hashimoto's thyroiditis
Graves' = autoimmune hyperthyroidism
Hashimoto's = autoimmune hypothyroidism
157
what are common triggers of Graves' and Hashimoto's?
stress factors
pregnancy
genetic predisposition
158
what happens in immune thyroiditis?
the infiltration by white cells (lymphocytic infiltration)
increased immunoglobulins within the gland
increased blood levels of thyroid antibodies
159
what are the key features of Hashimoto's in the blood?
presence of antibodies, the rise in TSH, and low blood levels of thyroid hormones
rise in TSH but normal fT4 = subclinical hypothyroidism
160
why is Hashimoto's disease frequently missed?
because of undue reliance on blood tests
= fT4 usually decrease but doesn't have to
= TSH usually rises but may be normal or low
161
explain what causes Hashimoto's thyroiditis but with normal blood test results
down-grading of the hypothalamic/pituitary axis due to the state of hypo-metabolism that the low thyroid function induces
- hypothalamus responds poorly to the low thyroid blood levels, and may not produce a normal level of TRH
- the pituitary, also affected, may not properly respond to the TRH = abnormal levels of TSH
- thyroid itself, being damaged by the white cell infiltration and with damaged TSH receptors, may well be less responsive to TSH anyway
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which test conclusively helps diagnose Hashimoto's and why?
antibody test
= any level of thyroid antibodies usually suggests an autoimmune process at work
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why may thyroid antibody levels decrease?
as the damage becomes chronis
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what causes hypometabolism in Hashimoto's?
low thyroid function induces
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what is the impact of hypometabolism in Hashimoto's?
- hypothalamus responds poorly to the low thyroid blood levels, and may not produce a normal level of TRH
- the pituitary, also affected, may not properly respond to the TRH = abnormal levels of TSH
- thyroid itself, being damaged by the white cell infiltration and with damaged TSH receptors, may well be less responsive to TSH anyway
166
how does mild Hashimoto's present clinically?
may be nothing obvious and only noticed during a general blood test
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what are the two ways Hashimoto's can present?
goitrous autoimmune thyroiditis (enlarging of the thyroid gland)
atrophic autoimmune thyroiditis (shrinking of the thyroid gland)
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explain how goitrous autoimmune thyroidits can occur
progressive lymphocytic infiltration enlarges the thyroid
white cells taking over the glandular tissue, the gland itself becomes a mass of fibrous tissue, with the follicular cells (where the thyroid hormone is made) disappearing
gland enlarges into goitre
sometimes = fibrous tissue takes over completely
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explain how atrophic autoimmune thyroidits can occur
antibodies block the TSH receptors in the thyroid and on the basis that what you don’t use, you lose, the glandular tissue shrinks
= thyroid gland shrinking with progressive loss of tissue
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what triggers goitrous autoimmune thyroidits?
lymphocytic infiltration of the of the glandular tissue
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what triggers atrophic autoimmune thyroidits?
antibodies block the TSH receptors in the thyroid
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differentiate between Hashimoto's and hypothyroidism
Hashimoto's = specifically autoimmune hypothyroidism
hypothyroidism = can have other causes besides autoimmune ones
(treatment same)
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differentiate between goitrous and atrophic autoimmune thyroidits
goitrous autoimmune thyroiditis = enlarging of the thyroid gland
atrophic autoimmune thyroiditis = shrinking of the thyroid gland
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what is the most common cause of hypothyroidism in the developed world?
a) subacute thyroiditis
b) Hashimoto's thyroiditis
c) thyroidectomy
d) drugs
e) iodine deficiency
b) hashimoto’s thyroiditis
most common cause of primary hypothyroidism in the UK
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what is the most common cause of hypothyroidism in the developing world?
a) postpartum thyroiditis
b) Hashimoto's thyroiditis
c) Graves’ disease
d) subacute thyroiditis (de Quervain’s)
e) iodine deficiency
e) iodine deficiency
iodine deficiency is the most common cause of hypothyroidism in the DEVELOPING world
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why does subclinical hypothyroidism present with raised TSH and normal fT4?
more TSH is needed to produce a normal level of thyroid hormone which is why TSH is slightly raised
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In Hashimoto’s thyroiditis which component of the thyroid gland are antibodies most commonly produced against?
TPO (thyroid peroxidase) = most commonly
but also thyroglobulin and TSH receptors
