Obesity Flashcards
What clinical features point towards a Cushing’s diagnosis?
- Recent rapid weight gain
- Tuncal or central obesity
- Fullness of face or “moon face”
- Increased blood pressure
- Glycosuria (associated with insulin resistance)
What are the clinical features of Cushing’s syndrome?
- Osteoporosis
- CVD (HTN, cardiomyopathy, atherosclerosis)
- Dyslipidemia
- Diabetes
- Obesity
- GH/GF1 axis impairment
- Myopathy
- Gonadal axis impairment
- Infections
- Peptic ulcer
- Nephrolithiasis
- Skin manifestations
- Cataracts, glaucoma
- Neuropsychiatric disorders
- Thrombophilia
What are the BMI weight classes?
Different weight classes are defined based on a person’s body mass index (BMI) as follows:
healthy weight: 18.5–24.9 kg/m2 overweight: 25–29.9 kg/m2 obesity I: 30–34.9 kg/m2 obesity II: 35–39.9 kg/m2 obesity III: 40 kg/m2 or more.
When do adults need to be referred to tier 3 care for obesity?
- the underlying causes of being overweight or obese need to be assessed
- the person has complex disease states or needs that cannot be managed adequately in tier 2 (for example, the additional support needs of people with learning disabilities)
- conventional treatment has been unsuccessful
- drug treatment is being considered for a person with a BMI of more than 50 kg/m2
- specialist interventions (such as a very-low-calorie diet) may be needed
- surgery is being considered.
Which group of patients should be considered for bariatric surgery?
Bariatric surgery is a treatment option for people with obesity if all of the following criteria are fulfilled:
- They have a BMI of 40 kg/m2 or more, or between 35 kg/m2and 40 kg/m2 and other significant disease (for example, type 2 diabetes or high blood pressure) that could be improved if they lost weight.
- All appropriate non-surgical measures have been tried but the person has not achieved or maintained adequate, clinically beneficial weight loss.
- The person has been receiving or will receive intensive management in a tier 3 service
- The person is generally fit for anaesthesia and surgery.
- The person commits to the need for long-term follow-up.
What is the dexamethasone suppression test? What is its use in clinical practice?
Dexamethasone is an exogeneous steroid that will cause suppression of the pituitary through negative feedback. It is used to assess the integrity of the hypothalamo-pituitary-adrenal axis. Dexamethasone binds to glucocorticoid receptors in the pituitary and thereby inhibits ACTH secretion by the pituitary gland. When testing the adrenal functions in patients with Cushings syndrome, Dexamethasone may be administered in low (1–2 mg) and/or high (8 mg) doses.
Low dose dexamethasone suppresses cortisol production in normal subjects. High dose dexamethasone suppresses steroid production in pituitary dependant Cushings syndrome - or Cushing’s disease. It will not reduce steroid production in patients with primary adrenal tumours or in those with ectopic ACTH production.
Normal subject: Reduction in cortisol levels following low-dose dexamethasone.
Cushing’s disease: No reduction in cortisol output after low-dose dexamethasone, but inhibition of cortisol output following high-dose dexamethasone.
Adrenal tumour or ectopic ACTH: No reduction in steroid production after low or high dose dexamethasone
In patients with high resting cortisol and ACTH levels, but with the ACTH levels being not suppressed with low or high dose Dexamethasone, ectopic ACTH secretion should be considered
What structure is anterior to the pituitary gland and can be affected in pituitary adenoma?
Optic nerve chiasm
What is bitemporal hemianopia?
A type of partial blindness where vision is missing in the outer half of both the right and left visual field. It is usually associated with lesions of the optic chiasm, the area where the optic nerves from the right and left eyes cross near the pituitary gland.
What pituitary tumours can occur?
- Non-functional adenomas
- Most common type
- Typically asymptomatic until very large in size
- Then experience headache, vision problems as it compresses on the optic chiasm - Prolactinomas
- Benign
- Increased secretion of prolactin: irregular periods, amennorhia, breastmilk production, erectile dysfunction, decreased libido, enlarged breasts, low sperm count, less body hair - ACTH-producing tumours
- Cushing’s Disease: fat buildup in face, neck, back, belly, chest; Arms + legs become thin; purple stretch marks; HTN
- Weakening of bones - Growth Hormone-producing tumours
- Acromegaly: extra growth in skull/hands/feet, deepened voice, change in facial appearance, wide spacing of teeth, joint pain, snoring/sleep apnea, diabetes
What is the effect of metyrapone?
Metyrapone is a pyridine derivative and a glucocorticoid synthesis inhibitor.
Metyrapone inhibits 11-beta-hydroxylase, thereby inhibiting synthesis of cortisol from 11-deoxycortisol and corticosterone from desoxycorticosterone in the adrenal gland.
What is the recommended test for adrenal function?
The recommended initial diagnostic tool to determine adrenal insufficiency (and gold standard for diagnosing primary adrenal insufficiency) is the short corticotropin test (also called ACTH stimulation test) with cortisol response measurements at 0, 30, and/or 60 minutes.
What are the biochemical abnormalities in Cushing’s other than cortisol levels?
Hypokalemia and hypernatremia
What 3 arteries supply the adrenal gland? Venous drainage?
- Superior suprarenal artery arising from the inferior phrenic artery
- Middle suprarenal artery arising directly from the abdominal aorta
- Inferior suprarenal artery arising from the renal artery
Venous blood is drained via the suprarenal veins with the right suprarenal vein draining into the inferior vena cava and the left suprarenal vein draining into the left renal vein.
As a result of the adrenal gland’s rich blood supply what is there a risk of?
The adrenal glands have a very rich blood supply and this accounts for the frequent metastasis of malignancies – such as lung cancer, to the adrenal gland.
In spite of this very rich blood supply, ischaemic necrosis of adrenals following prolonged circulatory shock – particularly in patients who have had severe post-partum haemorrhage, is a very well recognised clinical entity.
What functions do the cells in the zona glomerulosa, zona fasciculata and zona reticularis perform?
Zona glomerulosa: mineralocorticoids (aldosterone)
Zona fasciculata: glucocorticoids (cortisol + androgens)
Zona reticularis: androgens (DHEA)
Inner medulla: Chromaffin cells secrete catecholamines, adrenaline and noradrenaline.
How can primary adrenal tumours manifest?
- Glucocorticoid excess (Cushings syndrome)
- Mineralocortiocoid excess (Conn’s syndrome)
- Androgen excess
What are the tumours that arise from the adrenal medulla called?
Pheochromocytoma
Adrenal adenoma/carcinoma
What are the risks of long-term steroid use?
- osteoporosis (fragile bones)
- hypertension (high blood pressure)
- diabetes
- weight gain
- increased vulnerability to infection
- cataracts and glaucoma (eye disorders)
- thinning of the skin
- bruising easily
What are the causes of Cushing’s disease?
- Iatrogenic (steroid use)
- Primary ACTH
- Ectopic ACTH
- Primary adrenal tumour (ACTH independent)
Describe Cushing’s Disease
- Female:Male 3:1
- Age 25-45
- 70% of Cushing’s have pituitary ACTH producing adenoma
How do you confirm cortisol excess?
- Plasma cortisol (diurnal variation in secretion; stress responsive; sleeping cortisol levels are usually undetectable)
- Salivary cortisol
- Urinary free cortisol (urine sample)
- Dynamic tests (Overnight Dexamethasone suppression test; 2D Low Dose Dexamethasone suppression test) - Gold standard!
What other conditions/treatment can cause an increase/decrease in cortisol levels?
Raised in:
- Pregnancy
- OCP
- Suppressed in illness
What is the diagnosis from combined tests for adrenal function?
High dose Dexamethasone + CRH
Both negative = ectopic
Either positive = pituitary