Central hypothyroidism--various types of TSH responses to TRH stimulation.

Thyrotropin (TSH) levels in serum before and 20 and 60 min after the administration of 0.2 mg TRH i.v. as well as thyroid hormone (T3, T4) levels were studied in 39 patients with organic diencephalo-pituitary lesions and 27 healthy subjects. All participants gave their informed consent with the study. By the type of TSH response to TRH stimulation all patients were divided into 4 groups: 1. Normal response (n = 10): basal TSH 2.31 +/- 1.51, peak TSH 20 min after TRH 12.17 +/- 6.53, TSH 60 min after TRH 8.43 +/- 4.65 microU/ml; T3 2.02 +/- 0.48 and T4 95.9 +/- 27.73 nmol/l; 2. Blunted or absent TSH response (n = 8): basal TSH 0.82 +/- 0.42, peak TSH 20 min after TRH 1.51 +/- 0.66, TSH 60 min after TRH 1.35 +/- 0.51 microU/ml; T3 1.6 +/- 0.49 and T4 86.63 +/- 16.49 nmol/l; 3. Delayed ("diencephalic") TSH response (n = 16): basal TSH 2.69 +/- 1.27, peak TSH 20 min after TRH 7.96 +/- 3.35, TSH 60 min after TRH 10.0 +/- 3.97 microU/ml; T3 1.30 +/- 0.63 and T4 65.85 +/- 21.13 nmol/l; 4. Higher basal or stimulated TSH (n = 10): basal TSH > 10 mU/ml or stimulated values above 25 mU/ml. Mean T3 and T4 values in patients with normal or blunted TSH response did not differ significantly from the controls. Mean T3 and T4 in the group with delayed TSH response were significantly lower (P < 0.01). High TSH and low T3 and T4 levels were found in the patient with large meningioma sellae.(ABSTRACT TRUNCATED AT 250 WORDS)