Serum thyrotropin concentrations are lower in older than in younger patients with hypothyroidism
(July 2007)
The background of the study. Serum thyrotropin (TSH) concentrations increase in response to decreases in thyroid secretion. In this study, serum TSH and thyroxine (T4) were measured in a large group of patients with hypothyroidism to determine the effect of age on TSH secretion.
How the study was done. The study subjects were 578 patients with spontaneously occurring hypothyroidism. The diagnosis was confirmed if the patients had high serum TSH and low serum total or free T4 concentrations three or more weeks later or the initially abnormal values were normal during treatment with T4. Patients taking any drug that might cause hypothyroidism and those with a history of thyroid surgery, radioiodine therapy, external radiation of the neck, or childbirth in the past year were excluded. The patients’ serum TSH concentrations were analyzed in relation to their serum T4 concentrations and age.
The results of the study. The 578 patients with hypothyroidism included 460 females (80 percent) and 118 males (20 percent), ranging in age from 2 to 3 days to 99 years. Serum TSH concentrations were highest in the youngest age group, and declined with age, whereas serum T4 concentrations did not change with age (Table).
| Table. Serum TSH and T4 Concentrations in Patients with Spontaneously Occurring Hypothyroidism. |
| Age |
No. |
Serum TSH
(mU/L) |
Serum T4
(mg/dl) |
| 0–19 years |
9 |
100 |
3.2 |
| 20–39 years |
55 |
70.7 |
3.2 |
| 40–59 years |
159 |
49.5 |
2.9 |
| 60–79 years |
231 |
32.6 |
3.4 |
| 80–99 years |
124 |
24.4 |
3.7 |
| All |
578 |
39.5 |
3.2 |
Serum TSH concentrations were negatively correlated with serum T4 concentrations and with age, and were lower in the older patients when matched according to serum T4 concentrations.
The conclusions of the study. Serum TSH concentrations are lower, in relation to serum T4 concentrations, in older than in younger patients with spontaneously occurring hypothyroidism, suggesting an age-related decline in the sensitivity of the TSH-producing cells in the pituitary gland to a decrease in thyroid hormone production.
The original article. Carle A, Laurberg P, Pedersen IB, Perrild H, Ovesen L, Rasmussen LB, Jorgensen T, Knudsen N. Age modifies the pituitary TSH response to thyroid failure. Thyroid 2007;17:139-44.
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