Thyroid function during controlled ovarian hyperstimulation as part of in vitro fertilization

Capsule:
We report that ovarian hyperstimulation as part of in vitro fertilization led to significant elevations in TSH, often above pregnancy-appropriate targets. These findings were particularly evident in participants with preexisting hypothyroidism.

Authors:
Clarisa R. Gracia, M.D., M.S.C.E., Christopher B. Morse, B.A., Grace Chan, M.D., Samantha Schilling, M.D., Maureen Prewitt, R.N., Mary D. Sammel, Sc.D., Susan J. Mandel, M.D., M.P.H.
Volume 97, Issue 3 , Pages 585-591, March 2012

Objective:
To determine the exact nature and timing of alterations in thyroid function throughout controlled ovarian hyperstimulation (COH).

Design:
Prospective cohort study.

Setting:
University fertility clinic.

Patient(s):
Fifty-seven women undergoing COH as part of planned in vitro fertilization.

Intervention(s):
None.

Main Outcome Measure(s):
Timing and magnitude of change in serum thyroid hormones, including TSH, total and free T4, E2, and thyroxine-binding globulin (TBG), measured at six time points from before stimulation to 2 weeks after serum pregnancy test.

Result(s):
Geometric mean serum TSH increased during stimulation, peaking 1 week after hCG administration compared with baseline (2.44 vs. 1.42 mIU/L), as did free T4 (1.52 vs. 1.38 ng/dL) and TBG (32.86 vs. 21.52 μg/mL). Estradiol levels increased, peaking at hCG administration (1743.21 vs. 71.37 pg/mL). Of 50 women with baseline TSH ≤2.5 mIU/L, 22 (44.0%) had a subsequent rise in TSH to >2.5 during or after COH. The pattern of change over time in TSH concentrations was significantly influenced by baseline hypothyroidism and whether pregnancy was achieved.

Conclusion(s):
COH led to significant elevations in TSH, often above pregnancy appropriate targets. These findings were particularly evident in women with preexisting hypothyroidism and may have important clinical implications for screening and thyroid hormone supplementation.

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