Thyrotropin versus thyroid hormone in regulating bone density and turnover in premenopausal women.
OBJECTIVE
This cross-sectional study aimed to evaluate the interrelations between endogenous TSH level on one side and the status of bone mineral density (BMD) and bone metabolic turnover (BMT) on the other in pooled four groups of premenopausal women either without or with a long-term L-thyroxine treatment.


METHODS
Serum levels of free thyroxine (FT4), thyrotropin (TSH), calcium (Ca), alkaline phosphatase (ALP), osteocalcin OC) and cross linked N-telopeptide of type 1 collagen (NTx) as well as urinary calcium (U-Ca/24h), bone mineral density of lumbar spine L 1-4 (BMD-L) and femoral hip (BMD-F) were estimated in a cohort of 151 premenopausal women (median 36 years) consisting of four groups: Group 1, 40 healthy untreated women, while three other groups consisted of patients previously treated for about 5 years; Group 2, 41 patients with genuine hypothyroidism treated by L-thyroxine (50-100 microg daily); Group 3, 40 patients with genuine hyperthyroidism treated by Carbimazol (10-15 mg daily); Group 4, 30 patients treated by suppressive doses of L-thyroxine (100-150 microg daily) after thyroidectomy for thyroid cancer (n=10) or because of progressively growing benign goitre (n=20).


RESULTS
When using multiple correlation analysis (Pearson's r) in pooled 151 women, TSH showed significant positive correlation with BMD-L (p<0.01) and BMD-F (p<0.001) and, at the same time, significant negative correlation with serum level of BMT markers such as ALP (p<0.05), OC (p<0.05) and NTx (p<0.01), while the correlation of FT4 with BMD-L, BMD-F was significantly negative (p<0.001 for both) and that with all BMT markers was significantly positive (p<0.05 to <0.001). Thus, it appeared that higher TSH level was associated with increased bone mineral density and, at the same, with decreased bone metabolic turnover. These interrelations were further supported by the findings of significantly lower BMD-F (p<0.01), BMD-L (p<0.001) and significantly higher ALP, OC and NTX (all at p<0.001) in the group of 36 women with TSH level<0.3 mU/l as compared to the group of 115 women with TSH level range of 0.35-6.3 mU/l).


CONCLUSIONS
Irrespectively of thyroid diagnosis and/or previous long term thyroxine treatment in some groups, this cross sectional study showed that, after the pooled group of 151 women has been redistributed according to the actual TSH level, the bone mineral density and the level of bone turnover markers was significantly more favorable in 115 subjects with TSH level range of 0.35-6.3 mU/l than these in 36 women with TSH<0.3 mU/l.
Baqi
L
L
5th Clinic of Internal Medicine, Faculty of Medicine, Comenius University, Bratislava, Slovakia.
Payer
J
J
Killinger
Z
Z
Hruzikova
P
P
Cierny
D
D
Susienkova
K
K
Langer
P
P
D015502:Absorptiometry, Photon; D000328:Adult; D000469:Alkaline Phosphatase / Q000097:blood; D013956:Antithyroid Agents / Q000627:therapeutic use; D015415:Biomarkers / Q000097:blood / Q000652:urine; D015519:Bone Density; D016723:Bone Remodeling; D002118:Calcium / Q000097:blood / Q000652:urine; D002231:Carbimazole / Q000627:therapeutic use; D024042:Collagen Type I / Q000097:blood; D003430:Cross-Sectional Studies; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000378:metabolism; D006042:Goiter / Q000097:blood / Q000503:physiopathology; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood / Q000503:physiopathology; D007037:Hypothyroidism / Q000097:blood / Q000503:physiopathology; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000378:metabolism; D008875:Middle Aged; D015675:Osteocalcin / Q000097:blood; D010455:Peptides / Q000097:blood; D017697:Premenopause; D013959:Thyroid Diseases / Q000097:blood* / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy; D013964:Thyroid Neoplasms / Q000097:blood / Q000503:physiopathology; D013965:Thyroidectomy; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood* / Q000627:therapeutic use; D055815:Young Adult
D013956:Antithyroid Agents; D015415:Biomarkers; D024042:Collagen Type I; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; D015675:Osteocalcin; D002231:Carbimazole; D013972:Thyrotropin; D000469:Alkaline Phosphatase; D013974:Thyroxine; D002118:Calcium