[Anonymous]

#1050329

Clin Endocrinol (Oxf) 1998 Mar;48(3):285-290

Normalization of serum thyrotrophin by means of radioiodine treatment
in subclinical hyperthyroidism: effect on bone loss in postmenopausal
women.

Faber J, Jensen IW, Petersen L, Nygaard B, Hegedus L, Siersbaek-Nielsen K

Department of Endocrinology E, Frederiksberg Hospital, Denmark. e-fh@cybernet.dk

BACKGROUND: Patients with subclinical hyperthyroidism (reduced serum TSH and normal free T4 and T3 concentrations)
have slightly increased bone turnover and might have reduced bone mass, especially among postmenopausal women (due to
concomitantly reduced oestrogen production), as also seen during suppressive L-T4 treatment. OBJECTIVE: We have
evaluated whether normalization of serum TSH using radioiodine treatment (RAI) in postmenopausal women with a nodular
goitre and subclinical hyperthyroidism, protects against bone loss? DESIGN: Prospective, non-randomized study, outpatients
2 years follow-up. PATIENTS: Postmenopausal women with a nodular goitre, biochemically subclinical hyperthyroidism
(TSH < 0.2 mU/I, and signs of a growing goitre or compression symptoms. Sixteen were treated with RAI (median dose 555
MBq) (+RAI), whereas 12 were followed without treatment (-RAI). MEASUREMENTS: Serum TSH (third generation
technology), free T4 and T3 indices, and bone mass (BMD) as measured by Dual Photon Absorptiometry (4 in each group)
(only spine) or Dual X-ray Absorptiometry (DEXA) (both spine and hip), were measured yearly for up to 2 years.
RESULTS: The two groups did not differ regarding age, thyroid hormone parameters, and absolute levels of BMD at spine
and hip. RAI resulted in normalization of TSH in all 16 women, and FT4I as well as FT3I decreased to 78% after one year (P
< 0.01). These parameters did not change in the untreated group, thus serum TSH remained reduced. BMD at the spine
tended to increase (n.s.) after RAI to (median) 101.9% after one year, and 101.5% after 2 years. In contrast the -RAI group
experienced a continued fall in BMD to 97.3% after one year, and 95.5% after 2 years, both reduced as compared to the
+RAI group (P < 0.02). BMD of the hip also increased after RAI, to 102.3% after one year, and 101.7% after 2 years. In
contrast BMD in the -RAI group decreased to 94.8% after one year, and 98.0% after 2 years, both lower than in the +RAI
group (P < 0.01). CONCLUSIONS: Subclinical hyperthyroidism due to a nodular goitre in postmenopausal women resulted
in a continued loss of bone mass of about 2% per year. Radioiodine treatment resulting in normalization of serum TSH
prevented this continued bone loss for at least 2 years. Our study supports earlier intervention in such patients.

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