Post-partum transient thyrotoxicosis with painless thyroiditis.

5 patients presented with transient thyrotoxicosis and painless thyroiditis in the post-partum period. Thyrotoxicosis developed within 1-6 months of delivery. All had small non-tender goitres. Initially, all patients had elevated values for thyroxine (T4), triiodothyronine (T3) uptake, and triiodothyronine by radioimmunoassay (T3[R.I.A.]). Radioactive-iodine uptake (R.A.I.U.) was suppressed in all. In all patients, thyrotoxicosis resolved within 4 months; subsequent transient hypothyroidism occurred in 4, 1 developing permanent myxoedema. 2 had persistently elevated thyroid-antibody titres and needle-biopsy findings compatible with chronic thyroiditis. 1 became permanently hypothyroid. The other 3 patients had serial clinical and laboratory findings suggestive of painless subacute thyroiditis. Serial thyrotrophin-releasing-hormone (T.R.H.) stimulation tests are also reported. The importance of the low R.A.I.U. in recognising painless thyroiditis is emphasised. Since the disorder is self-limited, conservative therapy should be given.