Endocrinology Flashcards
Answer: Hyperthyroidism
Answer: Option D
In hypothyroidism the thyroid test shows decreased uptake which is indicative of hypothyroidism.
A 69-year old man presents with granulomatosis with polyangiitis (formerly Wegener’s) diagnosed about 8 months ago. He was treated with rituximab and prednisalone for induction remission and has required prednisone since his diagnosis.
- O/E: Temperature is 37C, pulse is 80bpm, BP = 150/90mmHg, RR = 14bpm, O2 saturation is 99% on room air
- His physical examination is notable for the findings in Figures A and B.
What would be the most likely electrolyte abnormality found in this patient?
Answer: Hypokalemia and hypernatremia
- This patient has exogenous (iatrogenic) Cushing’s syndrome. Hypercortisolism is a result of prolonged glucocorticoid therapy, which is the most common cause of hypercortisolism.
- The mineralocorticoid effect of cortisol results in water and sodium retention, and increased K+ and H+ excretion.
- Patients with Cushing’s syndrome could also have the following:
- Hyperglycemia: due to stimulation of gluconeogenesis enzymes (e.g., glucose-6-phosphatase) and inhibition of glucose uptake in peripheral tissue
- Hyperlipidemia (hypercholesterolemia and hypertriglyceridemia)
- Leukocytosis (predominantly neutrophilic), eosinopenia, thrombocytosis
Answer: Exogenous corticosteroid use
Exogenous corticosteroid use causes Cushing’s syndrome. A negative feedback loop stops the secretion of ACTH from the anterior pituitary, and therefore both adrenal glands become atrophic from disuse.
ACTH-secreting adrenal adenoma, as well as hyperplasia or carcinoma, produce high cortisol. The offending adrenal gland will be enlarged and negative feedback loop causes suppression of ACTH from the anterior pituitary and therefore the other adrenal gland becomes atrophic.
ACTH-secreting pituitary adenoma causes both adrenal glands to enlarge → excess cortisol causes Cushing’s syndrome.
Ectopic ACTH syndrome → excess ACTH causes increase the size of both adrenal glands - > excess cortisol causes Cushing’s syndrome.
Answer: Anaplastic carcinoma
Answer: Progesterone
Answer: IGF-1
Acromegaly is caused by an excess of growth hormone from a pituitary adenoma. It is diagnosed by testing for elavated GH and insulin growth factor (IGF-1) levels as well as a lack of GH suppression during an oral glucose tolerance test.
Answer: Testosterone
Answer: Hashimoto’s thyroiditis
Hashimoto thyroiditis is part of the spectrum of autoimmune thyroid diseases (AITDs) and is characterized by the destruction of thyroid cells by various cell- and antibody-mediated immune processes.
Patients with Hashimoto thyroiditis have antibodies to various thyroid antigens, the most frequently detected of which include anti-thyroid peroxidase (anti-TPO), antithyroglobulin (anti-Tg), and to a lesser extent, TSH receptor-blocking antibodies (TBII). Nevertheless, a small percentage of patients with Hashimoto thyroiditis (approximately 10-15%) may be serum antibody negative.
Clinical pearl: Hashimoto thyroiditis is commonly clustered with other autoimmune diseases, including pernicious anemia, adrenal insufficiency, celiac disease, and type 1 diabetes mellitus; be on the lookout!
Answer: Difficulty driving due to reduced peripheral vision
Answer: Sheehan syndrome
Sheehan syndrome involves necrosis of the anterior pituitary secondary to infarction. The anterior pituitary is particularly vulnurable to infarction due to hyperplasia of lactotrophs (without an increase in blood supply) during pregnancy. Typically, the posterior pituitary is not affected due to its differing embryological origin and therefore blood supply.
Answer: Zona glomerulosa of adrenal cortex
Zona glomerulosa = aldosterone
Zona fasciculata = cortisol
Zona reticularis = androgens
This specimen was taken from a woman presenting with hypertension, who was later found to have high serum aldosterone and low serum renin. What is the likely diagnosis?
Answer: Conn’s syndrome (adrenal adenoma)
A left adrenal adenoma is shown. Primary hyperaldosteronism is most commonly caused by adrenal hyperplasia and Conn’s syndrome (adrenal adenoma).
Answer: Waterhouse-Friderichsen syndrome
The image shows the black-red of haemorrhagic necrosis of the adrenal glands caused by Waterhouse-Friderichsen syndrome. This is typically caused by sepsis and disseminated intravascular coagulation due to Neisseria meningitidis infection.
Answer: Secondary hyperaldosteronism
Answer: Cushing’s syndrome
Answer: Hashimoto’s thyroiditis
Answer: Bradycardia
Clinical features of hypothyroidism are based on decreased basal metabolic rate and decreased sympathetic nervous system activity. These include myxedema, weight gain despite normal appetite, muscle weakness, bradycardia, cold intolerance, and decreased sweating.
The other signs and symptoms listed are consistent with hyperthyroidism.
Answer: Hyperaldosteronism
Increased aldosterone increases the secretion of K+ (hypokalaemia) and H+ (metabolic alkalosis) and absorption of Na+ (hypernatremia) in the distal tubule and collecting duct. The increased Na+ leads to increased plasma volume (hypertension).
Answer: Antidiuretic hormone
Peptide hormones include: insulin, parathyroid hormone, ADH, oxytocin.
The others are steroid hormones.
Answer: Pregnenolone
Answer: Cushing’s syndrome
Answer: Thyroid gland
Answer: Cushing’s syndrome
Cushing’s syndrome (hypercortisolism) causes excess cortisol. At high levels, cortisol cross-reacts with mineralocorticoid receptors and can thereby activate Na+/K+ pumps as aldosterone would, resulting in the net loss of K+ to the urine via secretion.
Note respiratory alkalosis can cause hypokalaemia.
Answer: Chronic renal failure
Renal insufficiency leads to decreased phosphate excretion. The increased serum phosphate then binds free circulating calcium, leading to hypocalcemia and subsequent stimulation of the parathyroid glands.
Answer: Graves’ disease
Answer: Parathyroid adenoma
Parathyroid adenoma causes most cases of primary hyperparathyroidism. It is a benign neoplasm usually involving one gland and typically presents with asymptomatic hypercalcemia.
Answer: Phosphofructokinase 1
Answer: Rheumatoid arthritis
Answer: PTH directly activates osteoblast which indirectly activates osteoclast resulting in hypercalcemia and decrease in phosphate reabsorption in the proximal convoluted tubules
Answer: Dexamethasone suppression test
Answer: Hypothyroidism
Answer: Follicular carcinoma
Malignant proliferation of follicles surrounded by a fibrous capsule with invasion through the capsule.
Answer: Exogenous steroids
Answer: Neisseria meningitidis
Waterhouse-Friderichsen syndrome describes haemorrhagic necrosis of the adrenal glands.
Answer: Cushing’s syndrome
Answer: Thyrotoxicosis
Answer: The likely diagnosis is diabetes insipidus
Answer: Hyperkalaemia is a complication
Hyperkalaemia occurs as a result of low aldosterone levels.
Answer: Autoimmune involvement of retrobulbar connective tissue, as per Graves’ disease
In Graves’ disease, an IgG autoantibody binds to and stimulates TSH receptors in the thyroid. The TSH receptor is also expressed on fibroblasts behind the orbit and overlying the shin. Activation of these fibroblasts results in glycosaminoglycan build-up, inflammation, fibrosis, and oedema.
Answer: Prolactin
A common presentation for hyperprolactinemia is amenorrhea. Important in the initial evaluation of amenorrhea is a prolactin determination. Oestradiol and progesterone typically are not measured in the initial evaluation of amenorrhea. Testosterone and DHEA-S are markers for androgen excess, which may be present in this patient, but do not need to be measured initially.
Answer: beta-1 receptors
Answer: Cretinism
Answer: Subacute granulomatous thyroiditis
Subacute granulomatous (de Quervain) thyroiditis is one of the few thyroid diseases that presents with tenderness of the thyroid. It typically follows a viral infection, causes transient hyperthyroidism, and is self-limiting.
Answer: Pituitary adenoma
Answer: Graves’ disease
Answer: Cortisol
Answer: Testicular and scrotal growth
Testicular and scrotal growth in boys are the earliest signs of puberty.
Answer: Low-dose dexamethasone suppression test
Answer: It commonly presents with pigmentation of the skin
ACTH is derived from precursor molecule pro-opiomelanocortin (POMC), which is also a precursor for melanocyte-stimulating hormone (MSH).
↑ Production of POMC (in order to ↑ ACTH production) → ↑ melanocyte-stimulating hormone (MSH) and hyperpigmentation of the skin (bronze skin)
Answer: Hypothyroidism
Hypothyroidism results from inadequate levels of circulating T3 and T4. The most common cause in countries with adequate iodine in the diet is Hashimoto’s thyroiditis. Clinical features are based on a decrease in basal metabolic rate and a decrease in sympathetic nervous system activity. Myxoedema occurs due to an increase in deposition of connective tissue components - glycosaminoglycans and others - which bind water, producing a non-pitting bogging oedema.
Answer: Phaeochromocytoma
Answer: Turner’s syndrome
Answer: Small cell lung cancer
This patient is presenting with obesity, striae, and hypertension in the setting of elevated cortisol suggesting a diagnosis of Cushing’s syndrome. Since the patient’s cortisol level did not respond to high dose dexamethasone, it is likely Cushing’s syndrome from an ectopic source such as small cell lung cancer.
Decreased ACTH level would describe a case of Cushing’s syndrome secondary to an adrenal mass which would present with an abdominal mass on CT.
Adrenal adenoma would also present with an elevated cortisol level that does not respond to high dose dexamethasone. A mass would be seen on abdominal CT.
Answer: CT of the thorax
This patient likely has an ectopic ACTH production from a tumour in the abdomen or thorax. High-resolution CT will localise the tumour in the majority of cases.
Dexamethasone suppression tests
The high-dose dexamethasone suppression tests help to distinguish patients with Cushing’s disease (Cushing’s syndrome caused by pituitary hypersecretion of corticotropin [ACTH]) from most patients with the ectopic ACTH syndrome originating from malignant tumours.
Answer: Haloperidol
Mechanism of action: Competitive antagonism of dopamine D2 receptors in the mesolimbic/mesocortical pathways.
Adverse effects: Marked extrapyramidal symptoms, hyperprolactinaemia, neuroleptic malignant syndrome. Note there is minimal sedative, hypotensive or antimuscarinic actions.
Answer: MRI of the pituitary
Answer: Low testosterone, low LH, and high prolactin
Answer: GH and TSH
Answer: Normal finding in pregnancy
Normal finding in pregnancy is correct. The total serum T4 level reflects free thyroxine (physiologically active) and T4 bound to TBG (physiologically inactive). Increased estrogen secretion during pregnancy stimulates the liver production of TBG. Thus, an increase in serum T4 in the presence of a normal TSH level indicates that the patient has an increase in TBG, most likely secondary to increased estrogen secretion during pregnancy. An enlarged thyroid gland and heat intolerance are normal findings in a pregnant patient.
Answer: Medullary carcinoma
Medullary carcinoma is a functional parafollicular (‘C’) cell cancer, secreting calcitonin. High levels of circulating calcitonin increase renal calcium excretion, decrease enzymatic activitation of calcitriol (1,25-dihydroxycholecalciferol), increase osteoblastic activity, and reduce osteoclastic activity.
Answer: Microadenoma
The serum level of prolactin correlates roughly with the size of a tumour. Prolactin levels greater than 300 are most likely associated with a macroadenoma. Microadenomas usually do not exceed levels of 200 to 300.
Answer: Low testosterone and low LH
Answer: Aldosterone
Answer: Prolactin
Answer: Hypothalamus
The hypothalamus is the body’s thermostat, detecting temperature changes and directing the autonomic nervous system accordingly. It is also involved in regulation of circadian rhythms and states of consciousness (receiving input from the eye and sending output to other hypothalamic nuclei, the reticular formation and the pineal gland), regulation of eating and drinking (the sensation of thirst is stiumlated when rising osmotic pressure is detected) and regulation of emotional and behavioural patterns (in collaboration with the limbic system).
Answer: Decreased peripheral resistance
Decreased peripheral resistance is correct. In elderly patients, hyperthyroidism places a severe load on the cardiovascular system. There is a decrease in peripheral resistance as a result of cutaneous vasodilation, and an increased incidence of atrial fibrillation.
Answer: Hypothalamus
Answer: IgG antibodies to TSH receptor are created, causing over-activation of the thyroid
Answer: Serum blood glucose
Serum blood glucose is correct. The patient has acanthosis nigricans, a skin response to chronic insulin resistance and high blood sugars (such as occurs in type II diabetes mellitus). Darkening of the skin, particularly along skin folds and around the base and back of the neck, occurs after a prolonged period of significantly elevated glucose levels. In addition to this skin finding, the patient’s obesity makes diabetes a more likely diagnosis. A simple fingerstick glucose check or serum glucose level could confirm insulin resistance; further workup may include fasting glucose, insulin levels, and haemoglobin A1c.
Answer: Prolactin
Answer: External carotid artery
Answer: Papillary carcinoma
Papillary carcinoma accounts for 60-70% of thyroid carcinomas. It typically presents in children and young adults.
Answer: Testosterone and dehydroepiandrosterone (DHEA) sulphate
Testosterone and DHEA sulphate is correct. Excess hair growth in females is due to androgens. As this patient has no signs of Cushing’s syndrome, androgen levels produced by the ovaries and adrenals should be obtained first.
Answer: Bitemporal hemianopia
Answer: ADH
Answer: Hashimoto’s thyroiditis
In Hashimoto’s thyroiditis, autoantibodies target thyroid peroxidase, thyroglobulin, and TSH receptors. Initially, this activity may cause stimulation of the thyroid gland and large release of T3 and T4, before the gland becomes fibrotic.
Answer: Weight loss syndrome
Answer: Conn syndrome
Answer: Renin-angiotensin
Answer: hCG
The first choice in testing in this patient is a pregnancy test. If her prolactin level was measured without a pregnancy test, an elevation of prolactin could be wrongly considered primary rather than due to pregnancy. The other tests of LH, estradiol, progesterone are not first choices in the evaluation of amenorrhea.
Answer: Pituitary gland
Answer: Option B
Low T4; high TSH; normal 131I is correct. The patient exhibits classic symptoms of primary hypothyroidism, probably secondary to Hashimoto’s thyroiditis. Hashimoto’s thyroiditis is an autoimmune lymphocytic infiltration of the thyroid gland. Decreased, serum T4 levels due to the destruction of the thyroid, and increased serum TSH due to lack of feedback control would be expected.
Answer: Thyroid lymphoma
People with Hashimoto’s thyroiditis are at an increased risk of B cell lymphoma.
Answer: Graves’ disease
In Graves’ disease, the uptake tends to be increased and more uniform.
Answer: Anaplastic thyroid carcinoma
Anaplastic carcinomas are undifferentiated malignant tumours of the thyroid usually seen in the elderly (mean age=65). They present as a rapidly enlarging bulky mass and often invade local structures (leading to dysphagia and/or respiratory compromise). They have an extremely poor prognosis.
Answer: Oestrogen therapy
Oestrogens increase thyroxine-binding globulin, elevating total T4 and T3, whereas free T4, free T3, and TSH remain normal.
Subclinical hypothyroidism (SCH), also called mild thyroid failure, is diagnosed when peripheral thyroid hormone levels are within normal reference laboratory range but serum thyroid-stimulating hormone (TSH) levels are mildly elevated. This condition occurs in 3% to 8% of the general population.
Answer: Jod-Basedow phenomenon
Jod-Basedow phenomenon occurs due to either overactivation of the entire thyroid gland or, more commonly, autonomous nodules within the gland after iodine repletion without adequate feedback control from the pituitary gland.”
Answer: Graves’ disease
Answer: Hyperthyroidism
Answer: Parotid gland and pancreas
Answer: Hashimoto’s thyroiditis
Thyroid peroxidase is a frequent epitope of autoantibodies in autoimmune thyroid disease, with such antibodies being called anti-thyroid peroxidase antibodies (anti-TPO antibodies). This is most commonly associated with Hashimoto’s thyroiditis. Thus, an antibody titer can be used to assess disease activity in patients that have developed such antibodies.
Answer: Nonthyroidal illness (sick euthyroidism)
Answer: Papillary thyroid carcinoma
Answer: Medullary thyroid carcinoma
Medullary thyroid carcinomas secrete calcitonin, arise in the calcitonin-producing parafollicular cells, and account for about 5% of thyroid cancers.
Answer: Graves’ disease
Graves’ disease is associated with related autoimmune phenomena in other tissues such as Graves’ ophthalmopathy in the orbit and pretibial myxedema in the skin.
Answer: Kallmann’s syndrome
Kallmann’s syndrome is a condition characterized by delayed or absent puberty and an impaired sense of smell. This disorder is a form of hypogonadotropic hypogonadism.
Answer: Hashimoto’s thyroiditis
Answer: Iodine deficiency
Answer: Insulin-like growth factor type 1 (IGF-1)
Measurement of a serum insulin-like growth factor-1 (IGF-1) concentration as the first step. A normal serum IGF-1 concentration is strong evidence that the patient does not have acromegaly. If the serum IGF-1 concentration is high (or equivocal), serum GH should be measured after oral glucose administration. Inadequate suppression of GH after a glucose load confirms the diagnosis of acromegaly.
Answer: Iodine deficiency
Answer: Toxic multinodular goitre
Patchy radioiodine uptake is common in multinodular goitre and Hashimoto’s thyroiditis, but hyperthyroidism with normal or increased uptake typifies toxic multinodular goitre.
