The 'hook effect' on serum prolactin estimation in a patient with macroprolactinoma.

Large quantities of antigen in an immunoassay system impair antigen-antibody binding, resulting in low antigen determination. This is called the 'high dose hook effect'. We report this phenomenon in a patient with a large macroprolactinoma. In this patient, the correct estimate of serum prolactin (PRL) was obtained only after appropriate dilution of serum. We suggest that in order to avoid the high dose hook effect, the serum PRL be estimated in appropriate dilution in all patients with large pituitary tumours. This is particularly important when the clinical suspicion of high PRL is strong, as in women with amenorrhoea-galactorrhoea and men with long standing hypogonadism.

Aetiology and treatment response in patients with spontaneous diabetes insipidus.

BACKGROUND: Spontaneous diabetes insipidus (DI) is an uncommon disorder. This study analysed aetiology and response to treatment in patients with spontaneous DI admitted to the endocrinology service of a teaching hospital. METHODS: Twenty patients were seen over a eight year period (1991-1998). The diagnosis of DI was confirmed in each case by the standard water deprivation test. Appropriate diagnostic procedures were carried out to determine aetiology. RESULTS: Sixteen patients had complete DI and four patients had partial DI. Eighteen had central DI and two nephrogenic DI. The etiology in sixteen of the eighteen patients with central DI included: histiocytosis--three, eosinophilic granuloma--two, neurosarcoidosis--three, viper-bite--one, head injury--two, germinoma--one, post RT--one, tuberculous meningitis--one, acute-sphenoid sinusitis--one and hypothalamic tumour--one. Eleven patients (61%) responded to tab. carbamazepine, while nine (45%) required intra-nasal DDAVP. One of the two patients with nephrogenic DI responded to thiazide diuretic. CONCLUSION: We identified the aetiology in 88% of our patients with central DI. Histiocytosis and sarcoidosis accounted for 40%. Most patients (61%) responded to treatment with oral carbamazepine, others required intra-nasal DDAVP.

Conn's syndrome: a simple diagnostic approach.

BACKGROUND: Primary aldosteronism is usually diagnosed after a battery of biochemical tests and adrenal imaging. If an adrenal tumour (Conn's syndrome) is identified, patients need surgery. However, bilateral adrenal hyperplasia is treated medically. Till 1994, we diagnosed Conn's syndrome using simple biochemical tests and a CT scan of the adrenal glands. Aldosterone and plasma renin activity assay became available in our institution in 1994 and were used subsequently in the work up of patients suspected to have Conn's syndrome. We analysed our data to determine whether simple tests such as serum and urinary potassium values combined with CT imaging of the adrenal glands are adequate to arrive at a diagnosis in these patients. METHODS: All consecutive patients (n = 17) diagnosed to have Conn's syndrome, managed by the Departments of Endocrinology and Surgical Endocrinology of this institution during a nine-year period from 1990 to 1998, were studied retrospectively. RESULTS: Until 1994, Conn's syndrome was diagnosed after documenting hypertension, hypokalaemia, inappropriate kaliuresis, metabolic alkalosis and CT scanning to localize the tumour. Serum aldosterone and plasma renin activity (PRA) were used in addition since 1994. All patients underwent adrenalectomy after adequate preoperative preparation. There was no operative mortality. Postoperatively, normokalaemia was established in all patients. Persistent postoperative hypertension was present in 43.8% of patients. CONCLUSIONS: In our experience, Conn's syndrome could be diagnosed accurately with simple investigations and CT imaging of the adrenal glands. Extensive biochemical testing, including aldosterone and PRA assay, is helpful when the diagnosis is uncertain. While hypokalaemia is curable after surgery, residual hypertension persists in about 45% of patients.

Systemic lupus erythematosus in Indian patients: prognosis, survival and life expectancy.

BACKGROUND: There have been several studies on survival patterns in Indian patients with systemic lupus erythematosus but it is still not clear as to which factors at diagnosis predict survival outcome. The impact of specific organ involvement, and of disease activity itself, needs to be studied further. METHODS: We conducted a non-concurrent prospective study of 98 lupus patients between 1981 and 1993. The clinical symptoms, signs and investigation results at onset, and at subsequent visits, were abstracted from the case notes. A systemic lupus erythematosus disease activity index (SLEDAI) was constructed at the initial presentation and for each subsequent visit. Patients not attending for at least 6 months were traced by post. The quantitative data from the SLEDAI was used to construct a Markov chain mathematical expression designed to predict life expectancy. RESULTS: The cumulative percentage survival at 1, 5 and 10 years was found to be 89%, 77% and 60%, respectively. The Markov chain predicted a life expectancy of 13.9 years. Central nervous system and renal involvement were poor prognostic factors. Proteinuria (> 0.5 g/day) caused a 50% reduction in life expectancy but increased disease activity at onset did not predispose to a poor outcome. CONCLUSION: The survival of patients with systemic lupus erythematosus continues to be poor. Central nervous system and renal disease indicate a poor outcome. Hence, new treatment strategies must be evolved to improve the survival of such patients.