two groups of patients undergoing total thyroidectomy one group received calcium and vit d prophylaxis the other group received no prophylaxis the investigator measured calcium level post and preoperative and development of tetant was recorded

This study is randomized controlled trial carried out on 86 patients undergoing total thyroidectomy in the period between January 2018 and November 2019. Patients were randomly allocated into two groups each one 43 patients the first group is the supplementation group where patients received oral vitamin D 40000 IU and calcium tablets 1 g once before surgery.

Patient included in this study are those above 18 years old undergoing total thyroidectomy.

Patients excluded from this study are those with

• Previous thyroid surgery
• Malabsorption diseases
• Pregnancy
• Previous parathyroid disease or surgery
• Vitamin D deficiency
• Renal impairment
• Hypo or hyper calcaemia
• ASA class 3,4

all patients in this study were subjected to thorough history taking full clinical examination, body mass index calculation, proper assessment of the original thyroid disease requiring surgery, preoperative investigations done as usual in addition to serum calcium, serum magnesium, serum vitamin D and serum parathormon level.

Serum calcium and serum parathormon were tested after 6, 12 and 48 postoperative hours, patients were discharged on the third postoperative day except if further hospitalization was indicated, after discharge patients were followed up in the outpatient clinic by one of the surgical team, serum calcium and parathormon level were tested after1 months, 3 months and after 6th months.

The primary outcome of this study is the development of hypocalcaemia either clinically or laboratory.

Clinical hypocalcaemia means development of perioral and \ or acral tingling and numbness, twitches of the perioral region on tapping in front of the ear" Chvostec's sign'', muscle twitches and development of carpopedal spasm.

Laboratory hypocalcaemia means serum calcium level below 8.5 mg\dl. Secondary outcome is the postoperative parathormon level. Preoperative data, postoperative clinical follow up and laboratory data were collected and analyzed using SPSS 22 program package.

Principles of total thyroidectomy; Total thyroidectomy was performed under general anesthesia, through lower neck collar incision, skin and platysma muscle flap was raised till the thyroid cartilage, opening the midline raphe, exploration of each thyroid lobe and tracing the inferior thyroid artery while emerging from underneath the carotid artery, the inferior thyroid artery was identified with its branches supplying the parathyroid gland, which was identified and preserved with its blood supply, the recurrent laryngeal nerve was searched for in the triangle between the carotid artery , trachea and the inferior thyroid artery. The external laryngeal nerve was identified and preserved 1 cm superior to the upper thyroid pole. If radical thyroidectomy was deemed the same principles of preserving parathyroid glands and their blood supply, recurrent and external laryngeal nerves. If the surgeons ere sure of damaging or removing the parathyroid glands a half of one of them was minced and transplanted in the subcutaneous tissue of the left forearm

Inclusion Criteria:

• patient undergoing total thyroidectomy

Exclusion Criteria:

• Previous thyroid surgery
• Malabsorption diseases
• Pregnancy
• Previous parathyroid disease or surgery
• Vitamin D deficiency
• Renal impairment
• Hypo or hyper calcaemia
• ASA class 3,4

the patients dont know what they received before the operation