Exploring the use of recombinant human TSH in the diagnosis of central hypothyroidism.
BACKGROUND
The diagnosis of central hypothyroidism (CH) is often difficult to establish as serum TSH levels may be low, normal, or slightly increased.


OBJECTIVE
To explore the use of recombinant human TSH (rhTSH) in the diagnosis of CH.


METHODS
Randomized single-blind clinical trial.


METHODS
Outpatient clinic of a tertiary care referral center.


METHODS
A single intramuscular injection of 0.1 and 0.9 mg rhTSH in random order with 1-week interval.


METHODS
Eighteen adult patients with pituitary insufficiency and six healthy age-, sex-, and body mass index-matched controls. Six patients had untreated CH (newCH), six had treated CH (CH), and six patients were TSH sufficient (nonCH). Five weeks before TSH stimulation, levothyroxine was replaced with tri-iodothyronine (T(3)) for 4 weeks. One week before stimulation, treatment was withdrawn.


METHODS
Thyroid hormones and thyroglobulin (Tg) before and 2, 3(1/2), 7, 24, 48, and 72 h after each injection.


RESULTS
In the newCH group, basal free thyroxine (FT(4)) levels were lower than in controls (P<0.05). After 0.9 mg rhTSH, the increases in FT(4) and reverse T(3) (rT(3)) were less marked in the newCH group than in controls (FT(4)+/-s.e.m. 9.2+/-0.5 to 19.7+/-1.2 vs 11.3+/-0.5 to 27.8.2+/-2.4 pmol/l, P<0.05). The CH group exhibited reduced basal and stimulated FT(4) compared with the TSH-sufficient groups. Tg increased similarly among all study groups after rhTSH injection.


CONCLUSIONS
In this pilot study, patients with untreated CH had lower response to 0.9 mg rhTSH in FT(4) and rT(3) than controls. An rhTSH test may be useful in the diagnosis of CH, but further studies are required.
Department of Endocrinology, Sahlgrenska Academy at Göteborg University, Sahlgrenska University Hospital, Gröna Stråket 8, SE-41345 Göteborg, Sweden. helena.filipsson@telia.com
Helena
H
Filipsson
Ernst
E
Nyström
Gudmundur
G
Johannsson
D000328:Adult; D000368:Aged; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000097:blood / Q000175:diagnosis*; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D008297:Male; D008875:Middle Aged; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000627:therapeutic use; D016037:Single-Blind Method; D013954:Thyroglobulin / Q000097:blood; D013963:Thyroid Hormones / Q000097:blood; D013972:Thyrotropin / Q000008:administration & dosage / Q000097:blood / Q000627:therapeutic use*; D014285:Triiodothyronine, Reverse / Q000097:blood
D007328:Insulin; D011994:Recombinant Proteins; D013963:Thyroid Hormones; D014285:Triiodothyronine, Reverse; D007334:Insulin-Like Growth Factor I; D013972:Thyrotropin; D013954:Thyroglobulin