Plasma free testosterone: equilibrium dialysis vs direct radioimmunoassay.

Direct determination of free thyroxin in undiluted serum by equilibrium dialysis/radioimmunoassay.

We have designed a re-usable dialysis cell and a complex dialysis buffer, with which undiluted serum samples can be dialyzed with minimal changes in their serum matrix. Dialysate thyroxin (free T4) is then measured by a sensitive RIA for T4. The range of reportability was 2-128 ng/L, the normal range was 8-27 ng/L, and the interassay CV was 7%. Free T4 concentrations in various disorders were a...

Direct radioimmunoassay for melatonin in plasma.

Radioimmunoassay of plasma testosterone, with use of polyethylene glycol to separate antibody-bound and free hormone.

We have developed a reliable radioimmunoassay for testosterone in plasma, polyethylene glycol ("Carbowax 6000") being used to separate antibody-bound and free hormone. Testosteron is separated from interfering steroids, notably dihydrotestosterone, by liquid-liquid partition chromatography on infusorial earth (Celite). The assay is sensitive (9 pg for standards), precise, and accurate. The lowe...

[Free testosterone index: comparison with plasma free testosterone].

Blood-free testosterone indices were measured among 28 normal men (age; 24-48 yrs.), 20 normal women (20-36 yrs.), 18 pregnant women (22-31 yrs.), 17 males with hypogonadism (23-56 yrs.), 17 males with chronic hepatitis (20-42 yrs.), 24 males with liver cirrhosis (29-68 yrs.), 34 males with hyperthyroidism (20-42 yrs.) and 7 hirsute women (18-31 yrs.), and these were compared with the plasma co...

Discrepancies between serum free triiodothyronine and free thyroxin as measured by equilibrium dialysis and analog radioimmunoassay in nonthyroidal illnesses.

We determined free triiodothyronine (FT3) and free thyroxin (FT4) in serum of patients with various nonthyroidal illnesses (NTI), by both commercial analog-type radioimmunoassays (A) and new equilibrium dialysis procedures (D). The mean FT3 was significantly lower in NTI by both techniques, but the decreases were of different magnitudes. The FT3(D):FT3(A) ratio was 1.96, vs 1.11 for healthy con...