GUIDE TO ENDOCRINE TESTING IN GENERAL PRACTICE

Abbreviations

Presenting Problem	When to Act (guidelines only)	Specific Endocrine Testing or "Screening Test"
Delayed puberty.	Small testes in boys 14y or older. No breast development in girls 14y or older. No menses in girls 16y or older.	Bone age, FT4, plasma LH/FSH, T/SHBG in boys. Consider plasma prolactin.
Hirsutism or virilising features.	(Severity often decided by patient).	Plasma T/SHBG (adrenal gland tests e.g. DHEAS, cortisol). Refer if plasma T>5 nmol/L provided SHBG is <30 nmol/L.
Menstrual irregularity.	(Clinical severity).	Pregnancy tests, prolactin, LH/FSH, FT4 (oligoamenorrhoea), (oestradiol); (T/SHBG if appropriate).
? Premature menopause (hot flushes before 45 y).	(Clinical severity).	(Pregnancy tests), LH/FSH, oestradiol, FT4, (prolactin).
Diminished libido (male) or impotence.	Persisting, without obvious cause e.g. drug-related.	Prolactin, T/SHBG, FT4 (LH/FSH, oestradiol).
Galactorrhoea.	If patient concerned, or if periods have stopped.	Prolactin, FT4.
Gynaecomastia.	Age-related. More important if post pubertal. Consider drugs.	Plasma T/SHBG, oestradiol, LH/FSH, prolactin, HCG, (FT4).
Infertility.	No pregnancy after 12 months.	Females - prolactin, progesterone (day 21-24 of cycle), LH/FSH. Males - sperm count, prolactin, LH/FSH, T/SHBG.
Unexplained fatigue, unexplained weight loss, anorexia (? cortisol deficiency).	Severity (lack of other cause).	0800 plasma cortisol, synacthen test (FT4, T/SHBG in males, LH/FSH, prolactin).
Fatigue, weight gain, high colour etc (? Cushing's Syndrome).	First clinical suspicion.	Overnight dexamethasone test, 24h urine cortisol excretion
Tissue overgrowth: enlarging hands/feet, excessive sweating (? acromegaly).	When suspicion first aroused.	Plasma IGF-1.
Unexplained or severe hypertension, e.g. Conn's syndrome or other adrenal disorders (Cushings, phaeochromocytoma).	1. If not responsive to usual therapy. 2. If recently acquired. 3. If plasma K is low. 4. If strongly episodic.	1. Ambulant (pre 10 am) upright plasma renin (PRA) and plasma aldosterone. 2. Consider renal cause.(MSU, U/S kidney). 3. Consider Cushing's (see above). 4. Consider phaeochromocytoma (urine catecholamines).
Disorders of plasma calcium (e.g. chance finding).	Abnormal plasma calcium level (when corrected for plasma albumin) in presence of normal renal function.	Plasma parathyroid hormone (plasma 25 OH Vit D). Fasting 0800 plasma calcium, phosphate and alkaline phosphatase.
Increasing skin pigmentation (? Addison's disease).	At first suspicion.	0800h plasma cortisol. Synacthen test, (plasma ACTH, PRA/aldosterone (ambulant, pre 1000h)).
? Pituitary disorder i.e. hypopituitarism (visual loss, or other suspicion).	At first suspicion.	FT4, LH/FSH, prolactin, T/SHBG in males, 0800h cortisol, (synacthen test,) IGF-1.
Abnormal thirst, polyuria, nocturia.	If sustained symptoms with no obvious cause	Arrange for 24h urine collection (volume), Further testing if volume >3.0 Litres/d in adults (refer).
"Whoozy" or confusional turns. ? spontaneous hypoglycaemia	On suspicion of spontaneous hypoglycaemia especially if occurring in the "fasted" state. (Symptoms occurring within 2h of food are unlikely to be serious).	Try to obtain both plasma glucose and insulin level during symptoms. Overnight (12h) fasted glucose and insulin (NB - finger prick glucose assays are unhelpful).
Unexplained hyponatraemia (plasma Na <135mmol/L).	Persisting, without obvious cause. Exclude drugs.	Plasma and urine osmolality and sodium concentration. 0800h plasma cortisol (synacthen test); FT4, (PRA, AVP). Consider chest x-ray.

 

 

Abbreviations

25-OH vit D	25-hydroxy vitamin D
ACTH	Adrenocorticotrophic hormone
AVP	Arginine vasopressin
DHEAS	Dihydroepiandosterone sulphate
FSH	Follicle stimulating hormone
FT4	Free thyroxine
HCG	Human chorionic gonadotrophin
IGF-I	Insulin-like growth factor I
LH	Luteinising hormone
PRA	Plasma renin activity
SHBG	Sex hormone-binding globulin
T	Testosterone